It was Thomas Riker in DS9. However, I guess I've always counted those two as the same guy in my head.

I saw previews of a Voyager episode where Q appears, and, for some reason, transports Riker aboard as well. Never watched it.

And, the final episode of ENT detailed the signing of the Federation Charter, and the last voyage of the NX-1701 under the command of Jonathan Archer. Riker and Troi were running the events of the episode itself in the holodeck, as a historical simulation. Riker played the part if the ship's chef. Alot of fans didn't like the way they crossed over with TNG as a last episode. But, I thought it rocked.

The ending was really sweet. Take a look...this begins as Riker and Troi are watching the signing of the Federation charter...