IRC Interview
Some sites will go as far as conduct interview in their IRC channels for potential members to come and seek an invite. The approach to doing this is to find out the irc channel via google and provided that there isn’t an irc key on it which most high level sites now implement join and wait for a mod. Most users resent this like myself when invite seekers come into the channel but ultimately it is up to the SysOp to restrict the access so it’s pretty much fair game. You might get an interview if you wait long enough and they might ask for ratio proof or speed. Most likely though you’ll get a test that determines whether or not you know enough about the content to be a member.

http://www.btracs.com – list of sites with open signups
http://www.trackerchecker.org – another list of sites sorted by signup status sites status and so on
http://filenetworks.blogspot.com – blog with updates on open signups reviews how to get invites etc
http://www.opentrackers.net – new web based open signup checker with rss updates etc