Ok, I know most mash ups just blow. Nevertheless, I love 'em. When you find one that works it makes it all worth it. And on that note, props to Arty Fufkin presents - very cool Mash Up Blog.
Has a great "Beastie Boys -Looking Down the Barrel of a Gun vs Sonic Youth, Kool Thing " mash up featured at the moment. The Zep meets Jackson 5 mash up on the other hand, well, noble effort
Worth checking out his site. And hey, got any more good mash up site, feel free to post them.