I remember playing RISK as a kid and always wanted to play on it on my TREO. Never did find a good version. Same with windows mobile. Finally, Lux Touch is just what I was looking for. The graphics are great, the interface for moving armies and attacking is easy and straight forward. To attack, you simply press on your target and hold down. The longer you hold down, the more armies per turn are used to speed up game play.
If you were to try this program on a smaller screen like blackberry or treo, I do not think it would work as well.
Now the good news and the bad news.. The good news.. Its free! The bad news... once you figure out how the A.I. works, and realize the A.I. make 1 mistake over and over again, it gets a bit easy to beat.