Got my XBox 360 a few weeks ago. I finally remembered that I have to register the 2 yr protection plan online. After 3 attempts with the damn web page timing out and making me re enter all the info, I've given up for the night. Tomorrow I'll try the toll free number which I'm sure will be at least 3 times as frustrating. If that doesn't work, I'll go back to the store with all the info and make THEM register it for me.
If you have a site in place, make sure it works!