I happened to win a $100 gift card to ebay motors at the challenge this year, and I've already put it to good use. A part for the challenge car (driveshaft collars), and a part for my tow vehicle (new bearings for my ford automatic running boards), and I still have $11 or so left to use.
ebay motors is one of the main places I buy and sell challenge parts, so thanks ebay motors for everything!