From StarryHeaven:
A short shoujo story about a girl who wants to continue the family tradition of her family…that is, get married at 16 and have a girl child at 17! A very crazy story about a very crazy girl named Ren who falls in love with one of the most popular boys in school, Juuya, at first sight!

From ClubManga:

Kayama Miharu enters her new middle school and immediately becomes friends with Mori Mizutama, a very cute guy she first takes to be a girl but is really a boy. However, though Miharu likes Mizutama, she cannot tell him, especially ever since the older Kawagoe (yes, a boy) seems to have taken Mizutama's interest instead. Miharu tries to be cute for Mizutama, but finds it practically impossible, as he is both more talented at home economics and more cute than herself. Then, Mizutama joins the Kawagoe's soccer club instead of the comedy-lovers' club the two of them had decided on earlier...

Also contains the story Fuyu Hanabi

4-koma manga

One day, an un-named ordinary high school girl (her name is left to your imagination), meets Cheko, a maid sent forth from a village of maids. Cheko the maid can melt, fly, remove her head and violate physics.

Surrounding the "ordinary high school girl" and her strange little maid are yuki-onna's who hate cold, a cute squid that can speak, moe yankees, tsundere maid assasins, ecchi lesbian teachers, trap yuki-otoko's, gentlemanly yakuza and many more.

[From AT-Translations]:

Based on an ero-game, Prism Palette is Peach-Pit’s (famous for DearS, Zombie Loan, Rozen Maiden and assorted other manga) first publication. It follows the main character, Masaki Shirai, as he spends his days at school, surrounded by beautiful girls.

From TJo:
TJO's 8th manga is Suzuki Noritaka's Shikotama, a comedy involving demons and more demons and uh, a little bit of snowboarding.

The sexy demon Mako has been sent from the demon world with an ultimatum mission from her father: bring him the "Supreme Soul," or else! However, getting the "supreme soul" proves to be a lot more problematic than Mako ever imagined as her friends fight back and a group of rival demons show up...

The guy who's always been by my side... the distance between us changes...

She calls herself Sexy Voice. To most of the world, she's just Hayashi Niko, an ordinary schoolgirl - but when time permits, she lives a double life as a hired investigator/spy. To help her, she has recruited the rather unlikely assistant she calls Robo, a geeky lump of a man who doesn't really know why he feels the need to do everything she tells him to. He just does it. Together, the odd team solve a number of cases for Sexy Voice's employer, an aging gangster.

Nanami Sekai gets scammed out of every penny he has, left only with a pair of boxers and a 3,000,000 yen debt. He then meets a girl, Ritori, who offers him a deal that seems too good to be true: she will take care of his debt if he will be her captain and help her with her job.

[Note]
It seems that this manga has been discontinued because the author became incapacitated during serialization and was not able to keep 2 series running.

A story about a 212cm military otaku with "Sensha Otoko" as his handle name. Despite his huge and imposing appearance, he is actually very shy, and thus had no girlfriends. One day, he saves a teenage girl from being harassed and promptly fell in love with the girl. However, because he has no experience in romance, he consults his otaku friends on the web-board Eirei Throne-Channel for advice. This is the beginning of a True Tank Story.Sensha Otoko - A True Tank Story is a parody of Densha Otoko that was part of the moon.cinemas.jp 2009 April Fools' Day joke. The manga was published in the Type-Moon 10th anniversary book, it was written and drawn by Haruno Tomoya.

From Chibi Manga:

Uta thought that her homeroom teacher was a geek, but she saw him when he was dressed differently. Sensei was actually a handsome rock-n-roll singer!? Since Uta had always wanted to have a boyfriend, she threatened him to "go out with her" and she wouldn't tell anyone his secret! but she ends up really falling in love with her teacher..!?

Contains:

• Natsu wa Ginga no Ame ga Furu
Summer Holidays. She didn't want to visit her grandmother, who she is on bad terms with, so she spends O-bon festival alone like she wanted. (Only for watching the house though!) And the person who appears in front of Akari is...!?

The Hanzo Academy is not just a regular school. It holds a top secret class for ninja training reserved just for the elite. Only two girls made the cut this year, Ikaruga, a quiet but gifted brunette, and Katsuragi, a passionate and skilled blonde. Their personalities could not be more polar opposite and sparks fly even on the first day of class. Ikaruga, being a little bit ahead of the curve, outscores Katsuragi on every assignment. With tensions running high, how will these two ninja students work together when the time comes?

When boys put their hands in their pockets, it means they're hiding their feelings!" Chiharu has a boyfriend that is very, VERY quiet. At first, she didn't mind at all that he rarely spoke because she believed that she was fine as long as their feelings could be conveyed. Soon, though, she comes to realize certain things that makes her feel extremely anxious towards him... Why does he always keep his hands in his pocket?

From Bluebird Scans:
The gyaru, Hana doesn't like the person that sits in front of her, Nioka and Nioka also hates gyarus?!

From JShoujo Scans:

1. Seishun Walker
Being a tomboy who loves to get into fights, Ouka's had zero-luck in the love department. The motto she lives by leans more towards "Be Yourself" than "Be Ladylike," and she follows that to a T. But lately, her long time friend Mashima's been on her case about how she should act "more like a girl"...

2. Appare!
Oumi Koutaro is a new high school teacher who just finished university. The students fell for him right away. All but Yonehara who already has a boyfriend.

3. Red-Green
Suzumoto Kureka broke up with her boyfriend. All left from their relationship is a red bicycle that they bought together. Even though she can't ride it, she takes it to school everyday, because she can't let go of her feelings. But one day the bike got sealed together with a green one. What does the owner of the green bike want from her?

1) Youth Survival
Summer camping trips are supposed to be filled with joy and laughter, but why is Kiriko so unlucky~~? At first it was that weakling four eyes, Kazuo and cutesy Hana-chan destroying the pork soup, but then they never came back after asking them to go pick up some wild herbs! Oh, fine! So she and Satoru went up the mountains to get them, but who knew they’d get lost too?!

2) Liar Love Letters
When Ritsu's boyfriend asks to break up, she complies - only to find that he's angry about it. To make her pay for dumping him so easily, he puts on a bet. Trick Ritsu into falling in love, and win a good amount of money. When she overhears this, Ritsu is determined to shoot down all the boys out to trick her. But what happens when she comes across someone whose lies capture her heart?

3) Sword and Heart: Dangerous Relationship
When you add the Japanese kanji character for heart underneath the character for sword, sword becomes the character for shinobi. Shizuru, when younger, had a crush on her very brave and handsome ninja senpai, and still likes him to this day. Things in her life get a little complicated when other ninjas decide to steal something valuable that her family is taking care of.

4) Never Dying Crow…!
Otokomae! Beads Club side story

About a sixteen year old girl who graduated in Australia and returns to Japan to teach English in a high school. The students are of the same age and so she has a lot of difficulties getting accepted by them.

Collection of short stories:
• Spring Egg
Chika’s house was actually just an old lodging house, but due to the location, her parents decided to turn it into a student dorm for the college students. One day, she meets her first love, Fujimori Tomohiro, a college student who will be living at her house! But, Chika’s mother had made him signed an agreement that he can’t go after Chika-chan?! How would their love bloom?!
• Sunflower Girl
Misaki likes Kenji but she doesn't have the courage to confess. Now that summer break is close, she plans to give him a love letter, but...
• Happiness Faces South!
Sakura used to like her sensei, but now that he has a girlfriend she decides not to like anyone else. Bon, a college student sees her playing softball and falls for her. Will Sakura be able to fall for him too??
• Prince and I
Mari has always liked her next-door neighbor Kaoru, but he always treats her like an old hag. Then Mari's sempai confesses to her. What will Kaoru do?
• 2 Block Honey
Satoshi's girlfriend used to be a crybaby, short and cute. That was a year ago! Now she's taller than him and likes to wear high heels. How does Satoshi feel?
• Spring, Air, Sunday

1-4. Seinen 14-sai / Seinen 14.5-sai / Seinen 15-sai / Seinen 18-sai
Itou just found out that one of his best friends, Machida, maybe kind-of sort-of likes him. He doesn't say it, but he did orgasm when thinking of Itou even as he was about to have sex with his girlfriend! Now, Machida has a complex about Itou and even kisses him, and Itou develops a complex about Machida because his first kiss was taken! On the edge of becoming men, will they figure out their feelings?

5. Neko ni Naritai
The son of an apartment manager falls for a tenant who keeps several cats.

6. Kakedasu Otoko
Two longtime friends sleep together and navigate the awkward fallout.

7-8. Hana to Ojisan / Boku no Ojisan
An author mourns the eigth anniversary of his wife's death, and comes to see his younger cousin in a romantic light.

9-10. Kanashii kara Janai
A sad child wanders into a tobacco shop, where a sassy shop owner gives him a cigarette. The boy and the shop owner become friends, and she helps him learn to make friends (including her grandson).

11. Seinen ?-sai / Extra

Toshiya is a university student who have always been attracted to older men. He enjoys the class of Kawashima whom everybody dislikes. Until a sudden turn of events and they start living together...

Nikumaru, meaning "meatball" in Japanese, is a seventeen-year-old student at Ninja High School, a special school for the training of ninja. He is short and chubby, but he possesses a super technique known as the "kamikaze", where he stirs up a whirlwind with his feet. The series introduces his many adventures and pranks as Nikumaru meets with his rivals both in and out of school.