Well, I obviously have my house's chant stuck in my head all the time:
D-E-L-T-A DELTA GO TRI DELTA
D-E-L-T-A TRI DELT'S THE ONE FOR YOU
WOOO HOOO!
But I also love Alpha Phi's silver and bordeaux chant (as does everyone else on this board, apparently).
Oh and Gphi's 'Flip Flop' has been stuck in my head since I heard it. If you need to have a song stuck in your head, here it is:
http://www.youtube.com/watch?v=zrPCpYs012U