Just noticed that Buy.com is now offering Free shipping on the $53.99 price.  Grab one before they run out or change the promotion.  This is currently the best Crackdown deal on the net:

• Buy.com
• Price:  53.99
• Shipping:  FREE
• Tax:  No tax in most states (Tax savings on a $59.99 game:  $4.20 (assuming 7% tax rate)) 
• Total:  $53.39
• Directions: 
1. Click here:  Crackdown $53.99 (w/ Invite to Halo 3 Multiplayer Beta!)