From Prisms:

A romantic comedy about Fuwa, a guy living in a small apartment in overcrowded Tokyo, who wants to have a place of his own. Because of a building accident in their new office building, Fuwa's company (5 employees) had to move into his apartment, right after he had moved to a larger place. And the new employee (Hiyama Izumi, a 15 year-old girl) had to move into Fuwa's place, as she had just come from the country. Then Fuwa's old girlfriend Tokiko, who had already gotten married, ran away from her husband and came to Fuwa's place.

From RebelliousArt:
Asahi, desperate after the loss of her best friend and boyfriend, came to the abandoned elementary school above the hill. It has been said that it's a cursed place that it will be the last place you will tread in. Those who live will not be able to return. And there, Asahi meets...!?

A series of oneshots.

Sana Kurata, a child actress, faces many problems in her classroom, including a major one - her bullying classmate, Akito Hayama. Sana's outgoing and friendly nature leads her to work towards correcting all of the problems around her. Her 'meddling' irritates Hayama but at the same time captivates him, just as Hayama's gloomy nature irritates Sana and compels her to change him. As these two opposites attract each other, they face many hardships which bring them closer to a mutual understanding.

This manga won the 1998 Kodansha Manga Award for shōjo.

Daisuke is a 23 year-old new schoolteacher. He ends up being put in charge of a 3rd grade elementary school class since the previous teacher quit, and in that class there's a girl who's quite a troublemaker--Rin Kokonoe. You could call her a masegaki (used to describe a kid that acts more like an adult in some ways), and she's also part tsundere (though more dere than tsun).

Peace seemed to have finally found its way into the Obinata household, but through an unexpected turn of events, Shuu and his adopted son, Yuuta, are faced with a disagreement that might change their forever. When their respective lovers, the eldest Obinata brother Taiga and Mayumi, the youngest, are dragged into their conflict, and Yuuta runs away from home, the whole family's living arrangement gets off balance. Will the peaceful days ever return?

Mainichi Seiten series:
Vol 1-2 Mainichi Seiten
Vol 3-4 Kodomo wa Tomaranai
Vol 5 Children's Time
Vol 6-7 Kodomo no Iibun
----Aki-chan no Iibun
Vol 8 Isoganaide
Vol 9-10 Hanaya no Nikai de

From Del Rey:

Najika is a great cook and likes to make meals for the people she loves. But something is missing from her life. When she was a child, she met a boy who touched her heart–and now Najika is determined to find him. The only clue she has is a silver spoon that leads her to the prestigious Seika Academy. At Seika she meets two brothers Daichi and Sora, could one of them be the boy from her childhood?

Won the Kodansha Manga Award for Children's Manga in 2006.

The son of a famous pianist, music student Shinichi Chiaki dreams of studying abroad and becoming a conductor like his mentor. Unfortunately, his fear of flying grounds his lofty plans! As he watches other classmates achieve what he has always wanted, Shinichi wonders if he should quit music altogether.
Then one day he meets fellow student Megumi Noda, also known as Nodame. This oddball girl cannot cook, clean, or even read a music score, but she can play the piano in incomparable Cantabile style. And she teaches Chiaki something that he has forgotten: to enjoy his music, no matter where he is.

Winner of the Kodansha Manga Award for Shoujo in 2004.

Yoshino Nako has a saying. "If I'm happy, I can do anything!"

In her sister's place, Nako-chan steals the groom of an arranged (political) marriage and helps them elope. But when the Hayami group starts failing, she must pay the consequence by housing the delinquent brother...

From Perfect Illusions:

Reo-chan, a first-year girl, gets dumped by her boyfriend because she's not skilled in the home economic traits he believes women should have. Her ex tells her that she must apply to a "housework" club before he will reconsider going out with her. Therefore Reo-chan has little choice but to join.

Here's the catch: the only members are four gorgeous bishies. The other first year in the club, Irinaka, competes with her a lot. As the story progresses Reo and Irinaka get forced into a lot of interesting situations together and in the meantime become closer and closer.

Being beautiful is never easy, especially if you're an eighteen year old boy like Yoon Da In who is constantly mistaken for a girl because of his delicate good looks. Da In is, in fact, anything but delicate. He is the ringleader of a group of tough kids in an all boy's school, and he's quick to beat the living daylights out of anyone who even hints that he resembles a girl. If that wasn't hard enough for a regular teenage guy to cope with, his life is about to take a shocking turn for the worse. When Da In stumbles upon strange happenings in the forest, he gets sucked into a world of vampire intrigue and sinister romance that he never knew existed. And he learns that there are worse things than being turned into a vampire: being turned into a girl?!

1) Tell Me More
Thanks to being of mixed race, with the bold facial features and nice body, you can say I'm popular with the opposite sex. However, guys don't seem to like my personality…that's why when I reveal my inner self, people might say “Your character is so different!” Lately, I've been chasing after Tsuchiya, but he seems to be like all the other guys…?

2) Look Cooler
I'm popular and every guy wants me because I'm cool, yet I'm going out with Tsuchiya, who is far from cool. I wonder what got me to go out with him in the first place? Suddenly he gradually became a little bit cooler....I think.

3) I Want To Go More
Recently Tsuchiya has been acting weird. He started to become cooler after his hair grew longer. Also, he stopped walking home together with me. No matter how much of an idiot he is, I love him.

4) Cherry Girl
My cousin Arata, came back from the U.S. He was tiny, slow and a crybaby. But now he totally changed. He greeted me with a kiss!? And the worst thing is, it was my first kiss!

5) Say I'm Cute
Just Because I'm in the Judo Club doesn't mean that I'm not girly. But Kazuki is the only person who thinks of me as a girl. I started to fall in love but he was already in love with another person, because of a delicious cake he ate, that was made by her. But the only thing he doesn't know, is that the cake was actually made by me.

Confident and in beautiful personalities develop projects for the Spartan models begins!

Twenty-nine-year old Kurose Kazumi is a programmer in an eroge company and has played plenty of galges when he was younger, but he's completely uninterested in young girls. A chance encounter changes that when a confused middle schooler approaches him due to a misunderstanding, but he realizes how sweet she is and wants to keep meeting her.

From StarryHeaven:

Best friends Tokieda Airi and Sahara Taki have had a happy junior high school life, but the mysterious group “F” begins to target them because they attract too much attention! “F” has already hurt many attention-grabbing students, and they begin their attacks on Airi and Taki by trying to split the best friends apart. When this method doesn’t work, they sink even lower: they target Airi’s sister Nako! Airi and Taki’s beautiful school life has been ruined, and now they must race to reveal the culprits of “F”…

From Nagareboshi Manga:
There's a new pet that has been found! It's called a baby, and Asahina Tamae is the only one in her class that doesn't have one. She finds three babies one day that seem to be special. They can do things that other babies can't! But before Tamae can keep them--she has to prove herself to her mother. Out of all her siblings, she gets the worst test scores, and the last thing she needs is another distraction.

Rikitaro is a musician whose dream is to become a rock star just like Jimi Hendrix or Jim Morrison, but at the age of 27 that dream is fading away rapidly.
Ooishi is a 3 time world boxing champion who recently retired and is now in the entertainment world, shooting a boxing reality show.
These two unlikeliest of people cross paths one day, but both of them think nothing of it until weeks later. Rikitaro is given one last shot by a record label to sign a deal but before that, they need him to get into better shape so that he is easier to sell. He stumbles upon a boxing gym which also happens to be the same gym Ooishi is filming his show.
As fate’s wheels start to turn, neither man realizes that they will work together to train the best boxer ever, even better than Ooishi himself.

"Save me!" Those were Sakurako Amamiya's last words to her friend Ageha Yoshina before she mysteriously went missing. Now Ageha's on a quest to find her. He's convinced that the mythical Psyren Secret Society has something to do with the recent rash of disappearances. And now he seems to be caught up as a player in their very deadly game...

From Aerandria Scans:

His highness the prince of Estolia Wilfred became an exchange student in Eito University. His noble appearance and gentleman’s manners quickly filled the campus with hysterical women’s voices. Miyako also studies at that university and for her master’s thesis, she is determined to interview the prince about his great-grandmother. But when she approaches him about it, she suddenly discovers “the dark side” of his character...?!

Contains Oneshot: Sinful Love ~ Your Future is Mine
Sequel of A Sin to Love You and A Sin to Love You~Can't Live witout You~ from Fu Junai

From Viz:
Ryoma Echizen just joined the Seishun Academy's tennis team, which is known for being one of the most competitive teams in Japan. Its members are incredibly talented, gifted, and athletic. With rigorous and extremely intense practices, the upperclassmen of the team expect the very best from themselves and they expect even more from the new members of the team. While most of the freshmen are on pins and needles hoping they won't get cut from the team, Ryoma Echizen is confident, cool, and collected. Some might even say he's cocky, but at least he's got the skills to back up his attitude. With his virtually unreturnable "twist serve," Ryoma is sure to make the starting team.
Join Ryoma and the other first years, as they train hard, make friends, and try to find a place for themselves on the team. And meet Ryoma's cute but chronically shy classmate Sakuno Ryuzaki. She's got a big crush on Ryoma, but will he ever notice her? Ryoma Echizen is the Prince of Tennis. He may be ready for the Seishun Academy tennis team, but are they ready for him?

Haunted by a space flight accident that claimed the life of his beloved wife, Yuri finds himself six years later as part of a team of debris cleaners on a vessel called the Toy Box charged with clearing space junk from space flight paths. The team consists of Hachimaki, a hot shot debris-man with a sailor's affinity for the orbital ocean; Fee, a chain-smoking tomboy beauty with an abrasive edge; and Pops, a veteran orbital mechanic whose avuncular presence soothes the stress of the job.

Note: Won the Seiun Award in 2002.