If you're looking for manga similar to Kaichou wa Maid-sama! Marriage, you might like these titles.
A one-shot collab between Hatta Ayuko (Ookami Shoujo to Kuro Ouji) and Mizuno Minami (Nijiro Days). Sata Kyouya is the school's guidance counselor and he has to deal with an odd group of students.
In order to help her father solve mysterious crimes, the student Susumi Fuji takes the identity of Maboroshi Panty.
A short gag "series" that Clamp draws in various magazines. Each involves xxxHOLiC and another CLAMP title.
Characters from various Type-Moon franchises, such as Fate, Tsukihime, and Kara no Kyoukai are able to hang out at the strange cafe called Ahnen Erbe. They chat together and deal with various curiosities such as a nosy talking cat or a "pot of happiness," which expels a gas that causes people to laugh.