Any reliable site where *hardware* engineers can be hired for small (work-from-home/telecommute) projects?
Elance.com and iFreelance.com both have listings for hardware engineers.  Elance is far larger, and currently has over 8500 providers listed under Electrical Engineering.  I am listed under both and have gotten work through them in the past.

Another one suggested by a comment below is freelancer.com, formerly known as getafreelancer.com.