You have until August 31st 2008 to register your EOS 5D with Canon and get the following benefits:
1. Priority Telephone Support
2. Exclusive Priority E-mail Support Address
3. $100 Voucher for Repair Service
4. 3 Day Turnaround Time for Repairs, and a 20% Discount on Service and Parts
5. Automatic Notification of Firmware and Software Updates via Email
Here is the link you will need to get to the registration page:
http://www.usa.canon.com/consumer/controller?act=OnlineRegModelFormAct&fcategoryid=703&modelid=11933