Where can you trade video games with other people

Goozex (now dead), 99Gamers and gametz.com are a few choices.

Here is a video of the first two (couldn't find one of the last).

Goozex: http://www.youtube.com/watch?v=F-8KEcWTwtI

99Gamers: http://www.youtube.com/watch?v=UHGOXQhW9ac