Full-time Hobby: It wasn't like electrical engineer David Hall [above] didn't have enough to do running his own company, Velodyne Acoustics Inc., of Morgan Hill, Calif., a maker of high-end audio speakers. Still, when he heard about the Grand Challenge, he decided to take a year off to enter. His modified Toyota truck finished third overall. Right: GhostRider with Anthony Levandowski. GhostRider fell at the starting line, but Levandowski is optimistic that in five years a descendant of GhostRider will triumph.