RvD2
OMG! This videos (RvD2: Ryan vs. Dorkman 2" is one of the coolest I've ever seen! Stop whatever you're doing and watch it.
The DIVX version has better resolution (if you can get it work). I didn't have much luck with it
If you liked that, you might try searching for star wars cut scenes or star wars fan film on youtube. You find things like Three In The Afternoon.
Also, it looks like the StarWars website is going to allow you make your own movie mashups.