Spaceref posts about the West Coast Human-Powered Vehicle contest being held April 13-15 at NASA Ames Research Center. The classes of vehicle are single rider, multi-rider, and utility. An East Coast version of the challenge will be held in Orlando at May 11-13 at the University of Central Florida. The contest comes courtesy of the ASME (American Society of Mechanical Engineers). Rules, Team websites, results from past years, and more can be found here.
This contest should not be confused with the Dempsey/MacCready Prize for "speedbikes" organized by the Human Powered Vehicle Association.