I've mentioned Code Monkey. Well, I'm also addicted to Shop Vac (aka why I will never go back to the suburbs again), Chiron Beta Prime (a holiday tune that everyone can identify with), and especially Skullcrusher Mountain (Isn't it enough to know I ruined a pony making a gift for you?)...and, also, Flickr, which really needs to be listened to with the accompanying video.
Seriously. If you like witty lyrics, if you like artists like Tom Lehrer, the Bobs, the Austin Lounge Lizards, Weird Al and They Might Be Giants, you need to check him out!