Another one I found:
http://wober.net
Total posts: 321,885
And another:
http://www.lifepunch.net/FORUMS/
Our members have made a total of 277,931 posts in 24,097 threads.
We currently have 7,786 members registered.
Another:
http://www.itsmods.com/forum/index.php
Our members have made a total of 101,250 posts in 9,562 threads.
We currently have 8,645 members registered.
Another:
http://www.workerscompensation.com/forums/
Our members have made a total of 208,843 posts in 14,108 threads.
We currently have 7,124 members registered.
Another:
http://forums.pcsx2.net/index.php
Our members have made a total of 303.181 posts in 35.051 threads.
We currently have 85.950 members registered.
Another:
http://www.networkedmediatank.com/index.php
Our members have made a total of 612,840 posts in 61,008 threads.
We currently have 116,549 members registered.
Another:
http://bring4th.org/forums/
Our members have made a total of 132,638 posts in 6,917 threads.
We currently have 4,808 members registered.
Another:
http://forum.xbmc.org/
Our members have made a total of 1,491,444 posts in 158,373 threads.
Another:
http://bluemoonroleplaying.com/forums/
Our members have made a total of 1,250,054 posts in 46,617 threads.
We currently have 15,896 members registered.
Another:
http://www.ofear.com/index.php
Our members have made a total of 100,029 posts in 5,134 threads.
We currently have 6,339 members registered.
Another:
http://www.frictionalgames.com/forum/index.php
Our members have made a total of 250,032 posts in 20,900 threads.
We currently have 13,495 members registered.
Another:
http://www.edulix.com/forum/index.php
Our members have made a total of 1,187,504 posts in 133,353 threads.
We currently have 206,474 members registered.
I'm done now, I think I got them all.