Classic short stories from Takahashi Rumiko. Many are comedies.

Volume 1:
"Fire Tripper" (fantasy, romance)
A gas explosion sends high school girl Suzuko and toddler Shuu 500 years into the past. But she lost Shuu on the way, and as a result, Shuu ended up in the past 10 years before her, and is 15 years old when Suzuko arrives.
"Maris the Chojo" (comedy, sci-fi)
A destructive alien policewoman sees a kidnapped quadrillionaire as her ticket out of debt.
"Those Selfish Aliens" (comedy, fantasy)
Aliens, the government, and fishmen implant bombs in a poor paperboy.
"Time Warp Trouble" (fantasy)
Warriors from feudal Japan inexplicably pop into a high-school classroom.
"The Laughing Target" (drama, romance, supernatural, tragedy)
When they were children, Yuzuru Shiga and his cousin Azusa Shiga were engaged. Azusa aims to make sure that Yuzuru stays hers, no matter what, but Azusa also has a dark secret...

Volume 2:
"Wasted Minds (Dust Spot)" (adventure, comedy, fantasy)
Follows a pair of two bickering government agents, both of whom have special abilities. (A five-part mini-series)
"The Golden Gods of Poverty" (gag comedy)
An unfortunate boy's scientist parents try to use him to make money, but they only succeed in contacting the Seven Lucky Gods, who happen to also be broke.
"The Entrepreneurial Spirit"
A woman leads seminars for a get-rich quick scheme.

Volume 3:
"That Darn Cat" (slice of life)
Takahashi Rumiko remembers having to take care of her neighbor's cat.
"When My Eyes Got Wings"
A couple befriend a sickly child with a secret and his destructive pet bird.
"Wedded Bliss" (comedy, romance)
A wedded couple can only let out their tension from working all day by fighting with one another, until their neighbors threaten to have them moved.
"Sleep and Forget"
A girl relives a past life involving her lover and an evil witch back from the dead in the form of a dog.
"A Cry for Help"
A fairy gives a boy a frightening split personality thanks to the wind-up key she inserts in his neck.
"War Council"
Student councils go to war with one another over a stamp.
"The Face Pack"
A man can change his appearance at will and leads a "masters of disguise" club.

more info here.

1) Rumble Rush
New worker at the train station, in a desperate situation being played with by a groper. A groper, who targets only young men during rush hours, appears! And… the new staff at the train station Akiyama, who by orders to become the bait for the groper, gets to experience the attack of the pervert finger…!!

2) Dr. H!

3) High School Maze

4) Roar of the Sea (Shiosai)
Hirofumi returns home when his father dies. Will he meet his high school friend Jin who confessed to him when they were teenagers and was part of the reason Hirofumi hasn't returned home for 15 years?

5) Stay

6) After the Rain

The story revolves around Tsukune Aono, a boy who accidentally gets enrolled in a school inhabited by monsters and demons. He quickly befriends Moka Akashiya, a vampire who soon develops an obsession with his blood, and later meets other girls who soon take a romantic liking to him.

From Attractive Fascinante:

After his parents passed away, Aizawa Kyouichirou, a middle third year high schooler, rented out the 6LDK apartment in the form of room sharing as suggested by his guardian, Yagi Akira. The occupants were Rio Forest - a foreign college student, Mutou Keigo – a National Literature college student, Kawakami Shinji – a top host and Tachibana Jinpei – a workaholic. After they started to live with each other, they learned how to love and care for each other.

From Fantasyshrine:

What happens when Nagasaku, the president of the most popular cafe "Lotus" and Kouzuki, the number #1 host of the most popular club "Adonis" want to rent the same 2.000.000¥ lavish apartment in the exclusive King's Hill? Room share, of course! Two unlikely roommates agreed to co-habitate the same apartment with very strict conditions. Will this arrangement really work out between these two semes...?

Being a housewife is no picnic, especially if you have to deal with an idiotic hubby, two reckless children, a mother whose hobby is to decapitate moving “things” and those annoying zombies that are always out to have the best bite of you. A hilariously bizarre tale from the king of gag manga: Kenji Hamaoka of Urayasu tekkin kazoku (Super Radical Gag Family) fame.

4 Stories---The first and second story have the same heroine.

She works at a daycare center or kindergarten, and unknown to her colleagues she used to be a much feared female gang leader. ^-^ Also, the heroine has good vibes about a certain male colleague. One fine day, she meets an ex-male gang leader who knows her past...and events start unraveling from there.

For the second story, it's set in the daycare/kindergarten too. The main character is one of the kids in the kindergarten, and he has a secret which he is afraid to let other people know, especially his beloved teacher. (The heroine is his beloved teacher.)

Story #3
The main heroine is a 16 year-old girl. Her father is a scientist and always invents some weird things. What's more, he claims that he came from another planet! All these drive the poor heroine crazy ^-^ But at least now her love life is going fine...until the day 2 guys from outer space land on Earth, wanting to find out more about the 'Love disease'! Perhaps her father has not been lying after all?

Shizuka, age 17, was raised by her mother, and the two are very close. However, the store her mom's worked hard to maintain was swindled by the Sakurasei Real Estate Company.
Shizuka then, pretending to be the new wife of the president of Sakurasei, enters the Sakurasei family home while the president is away on business to get back the deed to her mom's store. In an instant she becomes "mom" to three boys, and the eldest son Kanon is the same age as her...

From Enchantment Scans]: Zhui-Ming (Shina in original) is just an average girl. However, due to a makeover, she accidentally gets mistaken for popular idol, Ai, by another famous idol, You. What's this? Ai and You are supposed to be dating?What is going to happen to Zhui-ming? (found in the series Panic x Panic )

from Blissful Sin: The president of my company caught me, Chisato, kissing another man somewhere. Luckily, my company ranking is so low he shouldn’t be able to recognize my face! I desperately tried to convince myself of that, but several days later, I was selected to be the president’s secretary. This is horrible, it seems like the president knows about my relationship with men!

The story revolves around Wakame High School's extracurricular club, "Sexy Commando Club," which consists of 5-6 male members (one being the high school principal himself), a female manager, and a small mysterious pet (that may be extraterrestrial in origin). The strange and ancient art of Sexy Commando (the roots of which extend back into Japan's Muromachi period) is a martial one; however, instead of focusing on how to defeat an opponent with punches, kicks, or grappling, it focuses on how to distract the opponent. The logic follows that any distracted opponent is unable to fight, and therefore the art of Sexy Commando trumps any other form of martial arts. There are as many techniques as there are ways to distract, though Wakame High School's Sexy Command Club tends to employ the unzipping of the trousers (Elize no Yuutsu).

From ShoujoMagic:

All Kumiko wants is to become a teacher; however her father is dead set against it. He is giving her one chance to prove herself as a teacher before forbidding her from pursuing this career forever. Meet her newest student, Ryu-kun. He has NO desire to LEARN anything from his tutors, rather he is an expert at teaching THEM about...SEX?!

Note: The story was originally released as a single short story, but it later became a series.

All of the girls at his college love Suou Tsukasa and come up to talk to him on a daily basis. Unfortunately for them, Tsukasa hates girls that are straightforward like that, but is too nice of a guy to tell them that.

In fact, he has a crush on Kizaki Megumu, his classmate and one of the shy and least talkative girls. The professor in one of the classes they have together is Dr. Hime, a young teacher whose childish looks and short height makes her a target for her students to jokingly tease and treat her more like their friend rather than a professor.

After taking home the drunk Dr. Hime, who was served lots of alcohol by her students, Tsukasa learns a giant secret about her love life.

From Essence of Purity:

Takuma Ban, only son of the Ban familly from Hokkaido, comes to Tokyo on a quest: to find a fitting wife... with the help of Meari his cow. Jumping over a school fence while carrying Meari on his back, he unexpectedly meets a girl, Yuki Samejima. After one minute, he decides that SHE'll be his bride. Unfortunately for Takuma, Yuki's older brother, Ranmaru Samejima, is completely opposed to this.

Of course, the fact that Meari seems to have developed an instant "animal" attraction to him only reinforces Ranmaru's dislike of Takuma. Takuma is determined to make Yuki his bride and that, despite Ranmaru's stern "objections". Nevertheless, when not only Kei Enjouji but also Takuma's own family start getting involved, things get a little … "chaotic".

(Note: was originally debuted as a shounen manga, but Kodaka switched publishers and began writing it as BL)

From 801 Media:

Being with an older lover is hot on just so many levels... Seiji-kun is a novice manga artist. He's also completely addicted to the body of the incredibly beautiful Sono-san, despite the fact that Sono-san is a guy. Is this love? Along with the title story, one that paints a tale of youth and emotion, this volume is filled to the brim with stories of overwhelming density, including "Not Just When it's Convenient" and "Let's Go Home." A total of six stories in all.

• Onegai dakara, Kiss (w)o Shite (Please, Kiss Me)

• Otona no Tsugou ja Naikute (Non-Adult Situations)

• Gaki wa Sunao ja nee (Indirect Youth)

• Aiganbutsu wa Oheya no Naka (Trophies Belong in the Bedroom)

• Ouchi e Kaerou (Come Home)

From Attractive Fascinante: Sensei rejected Fuji when Fuji confessed to him on graduation day. After that, Fuji always visited sensei and they still went out together. Sensei realized his feelings gradually and hoped to start afresh with Fuji. However, Fuji couldn’t believe it. But when Sensei’s ex-lover, Namiki, came back and wanted to reconcile with Sensei, both Sensei and Fuji found that they could no longer hide their own feelings anymore.

1-2) Sensei to Himitsu
Kaji's woken up from his nap hearing popular Tsunoda-sensei getting hot and heavy with another guy! But it's his partner, the plain Aritou-sensei that Kaji can't stop thinking about. Kaji's eyes are being opened as he finds that the needs and dark desires that can bind together lovers aren't always about love...

3-6) Hold me for all of Time
A researcher, Sawatari Kaoru, runs off after finding out that there will be no more funding for his research. As he wanders around he sees an abandoned warehouse where he could use to continue his research with his remaining savings. As he walks inside the building, he meets an arrogant little boy. Surprise ensues as to the boys identity, and the unexpected result of his own research...

Extra) And then...
Continuation of ch.1-2, a little into their future.

On the once-peaceful planet of Industria, constant battles have been fought over control of the planet. Astro is a dim witted but kind boy who tirelessly works to feed his "family," a group of orphaned children. One day, after being fired from his most recent job, the prince of Industria, Bulge, appears in front of him. And even more shocking, Prince Bulge looks and sounds exactly like Astro! One thing leads to another, and Astro now has to take Bulge's place as the heir to the throne of Industria! Suddenly, he's faced with the task of bringing peace and harmony back to this war-torn planet!

- Red Hawk NEO

Compilation of short stories:

1) 1000 Years, I Love
Hakua is sent into the mountains by the village to kill a ferocious tiger that has been attacking villages. The tiger, mistaking him for a girl, drags Hakua into the mountains to become his mate. Love soon blossoms as Hakua must teach this half human creature the meanings of his new found emotions.

2) 1000 Years, I Love Extra
Their love going strong, Hakua decides to go back to the village. Naturally Youko tags along and runs into some trouble in the human world.

3) Lying Words Honest Kiss
A slave merchant Kouhaku steals a beautiful boy Enji to sell him to a public house. Little did he know that the boy wouldn’t mind at all.

4) Fallen Warrior
A doctor’s apprentice Suiki finds a wounded samurai in the forest and takes him to his home to treat. The samurai Genka is really bad-tempered and the boy has bad history with samurai.

5) The Flower of Love
Story about an artist Sekka and a beautiful boy Joka he saves who later comes to serve as his model.

6) The Path of Pure Love

[From Beautiful Soup]:

"Self Portrait" is the story of a boy dating a yaoi fangirl who puts him up in a bet with an older, homosexual photographer (And he obviously loses). Hilarity and shounen-ai ensue.

DMG via Renta!