Kyou Kara Maoh is like Ouran except the main character is a boy and a it's parody of shounen-ai anime instead of shoujo. There really aren't any serious romantic entanglements in this one either since the hero like Haruhi is pretty immune to all the wooing he gets.
Girl Got Game aka Power! has romance but it's so wacky that you really don't feel it for the majority of the manga. It's LOL funny like Ouran.
The first arc of Kare Kano doesn't necessarily remind me of Ouran overall but the main character is a pretty good female parallel of Tamaki.
In terms of appearance and characters, Fruits Basket is similar to Ouran except it has more depth and is quite a bit angstier.