D&D has an absolute wealth of campaign settings, (most) bringing their own flavors, tone and monsters etc.
So which one (or ones) are you most partial to?
I've never played in a campaign setting that wasn't made by people outside the group. So, even though I can't say I have experience- from what I read Eberron seems alright.
Has to be Pathfinder right now. Just loving my ranged monk. Flurry on a long bow for the win!