Although I’ve never been able to attend (being on the opposite side of the continent) I’ve always enjoyed the idea of Grassroots Motorsports Magazine’s $20xx Challenge. The basic idea being you build the best vehicle for under the year number in dollars. So $2010 for the year 2010. You then compete in an auto-x, drag race and concours show. The results are often amazing, crazy and inventive.
The Offical Event Page has results as well as some great video and photos.
Here are some build logs of some of the challengers: