From DrMaster:

All he ever hoped for was to be one step closer to becoming a priest, but Masato Kamioda gets more than he bargained for when he suddenly finds himself as the only male student in a pilot program at an all-girls divinity school.

Consists of 4 oneshots:

3) Devil's Baby-Sitter
Nao is saved by Shouji from a group of delinquents. However, Shouji himself is a delinquent and makes Nao his slave. But after a fight in which Shouji was hit in the head, he reverted back to his 7 year old self?!

From Chuu Chuu Train:

My class’s boys made some sort of group called O.P.D. (Mew Mew Group) and that stupid idiot “Shou”. Why do I always care about him? Why does he make my heart beat so fast? This sort of emotion is definitely not friendship… probably very special… Then that means I like–?!

From Aerandria Scans:

Kanako is an unattractive and not very capable office lady, until the day her mother passes away and she turns out to be the sole heiress of the old and elite Kinaga house. So suddenly, Kanako has not only to uphold her duties as an heiress, but to turn into an attractive lady so that she can marry accordingly to her new status. Thanks to the family butler and her own efforts, she manages somehow, but even in the middle of her newfound glamor, her world still continues to revolve around her butler...

From Aerandria Scans:
Arima and his little sister Chihiro are the twins of the Momoyama family. Six years ago, they've overheard their parents say "We will tell them the truth when they turn 16." The two worried that they might be adopted during those six years, but the truth they learn on their 16th birthday is even more shocking! Also includes an award-winning one-shot.

From Yen Press:

Welcome to the prestigious Saint Leaf School, where, among other things, the boys are so pretty they give the girls a run for their money! Amidst this bed of flowers exists one Hitomi Sakuragawa, a sweet girl with a not-so-little weight problem, who lives in a nearby apartment owned by her doting older brother. Hitomi also happens to have pretty much the best luck on the planet: Her neighbors are some of the hottest guys in school! But will she need to steel her willpower, cut out the cookies, and slim down before they’ll even give her the time of day? Or will they be charmed by her kindhearted, genuine personality? It won’t be long before Hitomi discovers that the road to a healthy lifestyle is paved with hilarity!

Tachibana Ritsuka is a female second-year high school student who attends Shiko Academy in Shiko Town. She enjoys her school life while living with her mother Maria, but one day, that balance falls into ruin when she discovers several of her attractive male classmate are demons.

A Collection of early stories:

From Covenant of Darkness:

Face, body, and talent, all 3 are what conspires Misako’s love for the star of the basketball club, with a genius ability and super beautiful Urasawa-kun. However, Misako's first and last profession of love in her lifetime was drastically discarded. Strangely, Urusawa-kun decided to model nudely for an art exhibition in hopes to winning a prize because he has an eye for that thing. The lingering affection is banned and the conditions that sends Misako's heart to abide… A romantic comedy treasure?!

From Sura's Place:
Cha Ji-Yyoung is a journalist who makes a terrible mistake and is forced to make amends for his fault. He is forced to crossdress and enter a woman's university to reveal corruptions. His interesting life as a 22-year-old female dancing student begins.

Teppei Arima is a second-year high school student who lost both of his parents in a traffic accident on their way home from a family trip. His grandfather, Isshin Arima, happens to wield the puppet strings in Japan’s vast economy and demands that Teppei becomes his successor as the head of the Arima Group. To prepare for his debut into high society, Teppei enrolls in an elite academy for the scions of the rich and powerful.

First Kurumatani Haruko Long series (no more a simple oneshot)!!! By Alessia-chan: Ruki is an otaku and is in love with a character of manga called Shun-sama! Suddenly she meet a guy that will live in her house due to her mother sudden travelling and that looks exactly the same as Shun-sama! But does this guy is really a prince-like such as Ruki expect?

This is the sequel to Violinist of Hameln. So read that first.

This series takes place in a fantasy world with famous composers' music, magic, friendship and dark secrets. Our main character of this story is a young ambitious, energetic boy named Schel. (Scale, as in the musical term) Because of the general of the MagiCorps saved Schel from a Mozoku (Monsters of this world) he has a dream to become the greatest magician ever. So he travels to the capital Sforzando the magic city and enters the MagiCorps School of Magic. There he meets Great, a violin magical music user, who is also the son of the great hero Hamel, who defeated the Demon King Chestra. As Schel tries to become the greatest magician, he also holds some secrets of his own. But how will Schel survive magic school with so many rivals to compete against?

One day, Toto—a 19-year-old virgin, obsessed with girls' breasts—found lying a naked, pretty girl (perfect breasts included), but who was completely without emotions. She learned to call Toto "master" and Toto named her "Kuu."

Kuu has a golem, which protects her from Toto's... advances. It also appears that Kuu has enemies who are after her for some reason.

Will Toto and Kuu make it in this romantic love comedy with a slight mystery? (Perfect breasts included.)

Kuragehime follows Tsukimi Kurashita, an 18-year-old who moved from Kagoshima to Tokyo to become an illustrator. Tsukimi is a jellyfish otaku who comes to live in a shared bath and toilet, women-only apartment, Amamizukan. Other tenants include fujoshi, NEETs and others who consider fashion their natural enemy, calling themselves "Amars". One day, Tsukimi meets a fashionable and beautiful girl, Kuranosuke Koibuchi, who saves a jellyfish that is about to die at a pet shop. She later discovers that Kuranosuke is merely cross-dressing in order to evade inheritance of his father's occupation as a politician.

Note: Won the Kodansha Manga Award for best shōjo manga in 2010 and was nominated for the 2010 Manga Taishō award.

Lucrezia, a noble vampire, has come to Japan to seek the supreme blood. However, when she encounters a poor shrine maiden named Inori, Lucrezia might have gotten more than she bargained for.

From September Scanlations:

With a father who's a singer, a mother who's a movie star, and an older brother, Shougo, who's the lead vocalist for the super-popular band The Crusherz, Sena Izumi, an otaku college student is the only dull one born into this super famous and talented family. He loves Magical Girl LalaLulu and is working hard to become a mangaka, but one day he winds up appearing in a TV commercial he just can't turn down. There, he's reunited with Ichijou Ryouma, the super-popular young actor he costarred with on a project ten years prior.

From Del Rey:
Little witch-girls Chocolat and Vanilla are best friends, but only one of them can be Queen of the Magic World. To determine who deserves the title, they must go to the Human World and enter a strange competition. Whoever attracts the most human boys wins! The girls had planned to be best friends forever, but both of them want to be Queen. Will their rivalry ruin their friendship?

Won the Kodansha Manga Award for Children's Manga in 2005.

We follow the bumpy and funny romance between bubbly Tamoko and the serious Kanji. With Kanji's father running an idol agency, and Tamoko being the daughter of their top-selling idol, Shinju, things get complicated. Tamako must hide the fact she is Shinju's daughter to save public face, and at the same time, she is determined to be Kanji's ideal wife (as was promised when they were little kids). It doesn't help that Tamako's pretty clumsy and poor of domestic chores, but no matter what comes down the road, she's not about to give up!

From Viz: What happens when an all-girls' high school reigning tomboy finds out her school is about to be filled with boys!? Hanabi Oozora is a rambunctious sixteen-year-old tomboy who comes to the rescue of her less assertive friends--sometimes in exchange for food. So what does she do when, all of a sudden, her all-girls' school is about to be integrated with an all-boys' school?! She meets and falls in love--naturally--with one of the three most popular and handsome boys in the Student Council, Yasuaki Garaku! Unfortunately, Yasuaki doesn't care for girls... and when the girls' Student Council clashes head-on with the boys' Student Council, Hanabi steps in to become a member - hoping she'll change Yasuaki's mind!

In one unusual Tokyo high school, education takes a backseat to brawling as warring clubs wreak havoc in the hallways and chaos in the classrooms, all vying to be the baddest team around! Although they often contribute their fair share, only a handful of students serve to stem the tide of violence in this untamed outpost. These are the few, the proud, the powerful: the members of the Juken Club!