well...I imagine most people are thinking "motor mount" or "clutch", but your description is a little thin.
Was the clutch replaced recently? Motor mounts are a frequent topic of discussion here, and replacing them solves alot of folks' problems. My mounts were bad enuf that all the cars in my rearview mirror were doing the boogie, so if you've eliminated other sources of a rough idle (like a vacuum leak), then mounts might be a good place to start; with your vehicle's mileage/age, they're gonna need to be replaced eventually anyway.
"I'm jealous of girls because they get to wear dresses." (Todd Flanders)