As Conrad told us in the early hours of this morning, Amazon is running a deal of the day for the Game of the Year edition of Borderlands. Flash forward to now, and you can see that they're offering sales for BioShock 2 and Mafia II.
The former is down to $10.99, which should be more than worth it, even if you're merely interested in checking out the Minerva's Den add-on. The latter, on the other hand, is currently half price at $14.99. Can't speak to the quality of Mafia II myself, but here's what Nick thought of the game.