The Grey Album (Jay-Z's Black Album over The Beatles' White Album) is really, really good. I don't really even like rap. But, man. "99 Problems" over "Helter Skelter" gave me chills. Seriously.
Would any of you Beatles freaks be interested in a zip? It's quite awesome and worth at least one listen.
ETA: "Piggies" under "Change Clothes". YOU KNOW IT CAN'T GET MUCH BETTER THAN THAT.