A while back, a couple of people posted some brief instructions and photos of the "home depot harness" in this thread: http://www.thedentedhelmet.com/f20/harness-help-20200/
I felt like this harness idea deserved its own thread, because it is very cost effective.
I followed their instructions and it turned out great. I highly recommend it. Total cost of materials is less than $20. Here are some photos.