Genes Reunited has mostly been a bust for me. I don't have a membership, so there may be more hot matches that are actually matches but haven't contacted me yet. I did find one person, but I'm not entirely sure how she connects to me and her info was on a lot of different sites.
Lost Cousins seems like such a good idea, but I've never had a match and I'm not holding my breath.
I've found a few people off of the trees and message boards on Ancestry. One was the grandson of my grandmother's sister, so a fairly close cousin. He had some cool old pictures. I've found two cousins, one of which my mother knows in real life, from their trees on their own webpages. I found a very distant cousin of my husband's on a MSN message board.