Colorado Trail Race - 530 miles of serious mountain riding (over 300 miles of singletrack and over 60,000 feet of climbing) through the Colorado rockies from Denver to Durango in July.
Each of these riders set a new course record in 2007 and every one of these was a very impressive performance. If you're not familiar with these events or riders take the time to read some of the above links. If you search through the race links and/or blogs you can find some race reports from these performances. Great stuff. Once you're done reading don't forget to come back here and vote in my poll.