Teresa Nielsen Hayden has been digging far too much into YouTube for grassroots political songs. Besides the Obama songs already mentioned by Phil, Teresa has found calypso, Makossa, five more Spanish songs, three raps, a torch song, vaudeville, etc. She also found two Clinton songs that are slightly better than the Laverne&Shirley knockoff that Phil found, a few McCain and Ron Paul songs, and several Huckabee tributes, including a heavy metal number called "Huck 'Em All" (yes, it's a tribute, not a parody). Go read Teresa's post and enjoy all of the links.
*I did it for you, Patrick!