AdrenalineHub.com 

Adrenaline Hub was a personal project of mind and one of the first Drupal sites I made. It aims to be a My Space/Faceface like social network for action sports fanatics.
The site uses a custom version of Drupal 4.7 with many patchs and extensions added to the core to aid performance. There are also a large number of custom modules being used on the site.