This guys got a few cool mashups. He has his own series of mashup albums called Bangfest, but at times he gets a little too electronic for my taste. Here are two of the best songs from the album. Ludachrist's website-->
Soul on Ice - This is really really good. Basically uses "Cold as Ice" as a sample for "Soul Survivor"
The Legend of Curtis - This is a pretty cool mashup of Zelda and 50 Cent's "Little Bit". Let The Beat Build on this one