I'm surprised no one has talked about okcupid.com . That's the best dating site I've used, period, and it's 100% free. They also run crazyblinddate. They have forums, chat, email, the best hi res photo gallery, a journal section, user created tests and games. I've met like 20 people because of it, a lot have turned out to be great friends.

One of the cool things about it is that they encourage use of the site through user generated content and by giving you a completion status. So most girls/guys try to get to 100% complete. But you get there by making a unique and interesting profile. So you get far less, "I'm looking for a laid back significant other who is goal oriented and has a great sense of humor." generic blah blah blah.