Currently, all the campaigns I'm involved in are D&D campaigns. That's hopefully a temporary thing, though - I have played dozens of different games in the past, and will hopefully get to play dozens more. Some of the better ones I've played in the past are Alternity, Earthdawn, Ars Magica, Call of Cthulhu, and the swedish games Drakar och Demoner, Mutant (various versions that are radically different), and Eon. Some of the games I hope to get to play/run some day are Shadowrun 4th, Exalted, Arcana Evolved, and Iron Heroes.
Some people in my current gaming group are a little resistant to learning new systems, though. I hope to be able to break them of that.