Lots of random little great deals have popped up post Christmas for you to spend any left over (or newly received) monies.
For those that don't have it still, Halo 3 is only $29.90 at GoGamer.
GameFly is having a Year End Sale up until January 4th: Some example deals are The Darkness only $12.34, Forza 2 $14.24, and Shadowrun for $12.34. I would really check this link and look into their full list, they have a ton of deals on all systems.
For the PC users, Steam is having a sale, 10-50% Everything! Great deals include, The Orange Box - $37.45, Bioshock $37.45, S.T.A.L.K.E.R. - $22.45, and Psychonauts - 9.95!! (If you haven't played this title yet, you have no excuse not to now. You can even use a 360 controller.)
World of Warcraft - $9.99 at Amazon.