Gosh, this takes me back to the good ole days of Tech TV when that show Eyedrops was on the air. Nothin' but animated shorts (I think all CG, but I could be wrong about that). It was only a few years ago, but it seems like forever.
I love Harry Partridge's stuff, and this is just a taste of his great work:
EDIT: I found what I originally wanted to put, the work of Don Hertzfeldt. One of my favorites and the one that got him an Oscar nom: