Are you looking for opened Private Torrent Trackers
Most of the Private Torrent Trackers have some user limit and if the user limit is exceeded then they’ll close registration. If you wanna register with those web sites you may need to wait for some time, till some inactive accounts get deleted.
It’s a pain to track them and check them every day to see whether they have opened for registration or not.
I found this interesting site, where it tracks the private trackers and let you know about the sites where sign-up is open.
WARNING: Some adult advertisements are displayed when I checked the site, so don’t be embarrassed by opening it in public places such as library.