This is an insanely good deal going on at Amazon.
You can pick up a copy of Bioshock for the Xbox 360 for $56.99 and get a copy of The Darkness essentially free. Free shipping and no tax.
An IGN review of BioShock is here, http://pc.ign.com/objects/707/707640.html
It looks like an awesome game. It's also available for PC, but I don't think there's a combo deal for it like there is the 360.