Oh yeah, there is quite a few:
Spice and Wolf. That was quite unique idea, but perhaps thats why it got 2 seasons (in a way that it was boring or something). I am currently collecting all light novels.
The Melancholy of Haruhi Suzumiya. It was quite a hit, not sure why hey dont do it anymore. They adapted like only half of the light novels, but damn even novels are right now out of print, especially the last 2 ones, so its quite hard to collect right now.
School Rumble. This anime was so hilarious. Too bad they adapted only the ending of the manga and completely skipped 3rd season.
Great Teacher Onizuka. I am not sure, but manga has a lot of volumes and anime ends with no real closure, so I guess there must be more.
The Knight in the Area and Over Drive. Very much enjoyed those two sports anime, quite interesting, but nobody even translates the manga, so I cant get closure.