At Dreamforce, we were told that the Registration process was built with the Sites.com platform. Can you explain how it was done for Dreamforce ?
Sites provides seamless integration with Customer Portal and PRM portal products for authentication. You can find an example in chapter 14 of the new the Developer Guide: http://wiki.apexdevnet.com/index.php/Force_Platform_Developer_Guide. If you sign up a new DE org, you will be given 10 Portal users in your DE org to test with.