My girlfriend and I decided in early January that we wanted to do the AIDS Lifecycle ride from San Francisco to Los Angeles. All 545 miles.
At first we were going to do it alone, but after telling a few people and getting excited about the ride we eventually ended up riding with 8 people. We bought bikes, sent out our fund raising letter and committed to the ride. After 3 months of training we finally finished. I have to say it was life changing. If you ever get a chance to go, it's a great way to see California, give back to a good cause, and get a little (Really a lot) of exercise at the same time.