GameStop is offering early access to the Left 4 Dead demo for those who preorder Valve's upcoming multiplayer zombie shooter (thanks Mike Martinez and Gamers Platform). The Xbox 360 and PC listings both carry the same offer:

Reserve Left for Dead and receive early access to the demo. The early access will start on 11/6/08 and will end on 11/11/08. Offer valid only while supplies last.

In-Store and Online Customers: Codes and instructions will be emailed beginning 9/5/08. You must provide a valid e-mail address at time of online order or in-store reservation in order to receive an early access code.