I've tried pretty much every free one.
DateHookup: I'm not sure if this one is even around anymore, but I did make a connection for a short while with someone though it ended up going sour after a month because we lived too far away from each other. There were lots of trolls there but also some nice people. I also got a stalker from there too though. =/
Plenty of Fish: I made at least one close friend, but no dates. This site had the least amount of trolls.
OKCupid: I had dates planned but never followed through with any of them for various reasons, usually not related to the person there. I consider this site the best for meeting people of the free ones.