I'm a big fan of Carl Stalling's music written for Warner Brother's cartoons, especially Bugs Bunny. The Merrie Melody theme is an American classic. The idea of great big orchestras playing complex music for cartoons is pretty cool.

I also love the musical intro to The Jetsons and The Simpsons. (Check the version with real people. Also, here's the original version.) And the Simpsons' take on the Flinstones Theme is pretty good too. At least one of these will be stuck in your head all day. (All via YouTube)