Here is some good news for your. Torrent-Damage, a well respected private tracker has been accepting new users in the last few days (without invites). TD has nearly 40000 users and over 21000 torrents indexed, in addition to the decent pre times.
The reason why we say they have 'occasionally' opened signups is that you may have to try several times to get in since they have not increased the user limit (40000). But they do seem to be actively purging obsolete accounts in the last two days, making new slots available to new members. At time of post, there are 15 slots available. This may increase and decrease as new users signup and as TD admins delete more accounts. You may need to try several times to get in but they do open signups.
Site Name: Torrent-Damage
Signup URL: http://www.torrent-damage.net/signup.php
Signup Notes: Leave ticket number blank.If you get the user limit reached message, keep trying. We cannot guarantee anything but there is a good chance for you to get in.