Well there's the all well-known (with sexual content... make sure you are not a minor!) Junjou Romantica Papa to Kiss in the Dark An anime one-shot called Sensitive Pornograph... Gravitaton (Not much...
Okane Gai Nai is one of my favs (No Money in english) and Papa to Kiss in the Dark and Tsukiyono Fushigi is good as well. Haven't read many but they have good plot. Junjou Romantica is Great also....
Well, it depends on your taste. Some people like well-developed characters and plot, and some readers just go for the sex scenes. Some well-liked titles: Junjou RomanticaGravitationZetsuai...