Brothers Akira and Suguru love to cross-dress and have no qualms about showing their panties, something their neighbor Hiro tries to prevent.

For high school girls there are some "battle days", for example Valentine's Day, Christmas, and...

After being awarded the Nobel Prize, child prodigy Alice T.P. Riida runs away from home and creates the first Artificial Human, Ninomae Shii. Along with Shiratori Jun and Kurosaki Yaoki, Shii now struggles to find out for what reason he was made for.

Marimo has a job to do... but it's too cold and she doesn't want to leave the kotatsu.

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.

Mizuho can't believe his ears when Grandpa's will is read out. Grandpa's final wish is for Mizuho to attend the same academy as Mizuho's mother. The catch is it's an all-girls school. With the help of his friend Mariya however, he gets a makeover good enough to fool everyone at the academy.

Nao, Yuki, Tomo and Rio are four brothers working as maids in their family's maid cafe Cherry Girls.

From SnoopyCool:
A young man has been cursed, and a wandering Shrine Maiden has come to his school to further her demon-fighting techniques. How will she save him?

Wakaba Chiharu is a fujoshi, but hides it from her friends. She fantasizes about male classmates being intimate and uses them for her manuscripts. But somebody is interfering with her daydreams...

Yuusuke & Akira used to be childhood friends, but haven't seen each other in 10 years after Akira's father was temporarily transferred for his job. Now cute Akira has come back and is living next door, and she's looking to keep Yuusuke to the promise he made to her when they were little.
The problem? Akira is actually a guy!

Basically, the teenage detective kiddo was frozen by some EVIL MASTERMIND PROFESSOR back in near-mid-1900’s, and gets unfrozen in the 2000’s by his granddaughter. Hilarity ensues as he encounters weird new stuff and does silly blunders in his daily life with his granddaughter, Hikari.

Really short like 4 pages

Inukai Shirou a male high-school student leading his life when suddenly his dog Mashiro turns into a human girl and now he must satisfy her wants or face the consequences.

At a sport festival and upcoming calvary battle, the boys cheat and use a tactic of dressing up one of the boys into a girl to throw everyone off their game.

Sugano Ikkei is a typical teenager at his high school and lives with his older brother Hyakkei who is an editor at a publishing company. Hyakkei is in charge of several artists and writers and his job is to support them in anyway possible. However, he broke his leg and is unable to leave the hospital for a week and he has a very important meeting with a very shy writer named Tokito Aona which has taken months to get a face to face meeting. As they look really alike, he asks Ikkei to dress up as him and go as Hyakkei. The meeting goes well without her knowing the truth, but Ikkei is forced to go to another meeting with Fujimaki Misuzu, an artist moving to Tokyo in order to continue working. To his surprise, both girls, Tokito and Fujimaki, are in the same class as he. Now he has to juggle being Hyakkei as an editor to the two girls as well as be their classmates as Ikkei, and do all this without letting out the secret that he is the same person.

She's the most popular girl in school, but what all the guys don't know about Akari is that she's actually a yaoi-crazed doujinshi artist... and her subjects look an awful lot like some boys from school. from snoopycool

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...

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.