It is called Tolkien Forums. It is relatively new but is quite large, very nice layout and has got quite alot of features. I recommend it to all
serious Tolkien Fans as its forum content is often quite advanced Lore but it also serves good for more laid back members as well becuase it has more laid back Forums like RPGs, trivia and debates. It is 100% worth becoming a member as its all free!
Here it is -
http://tolkienforums.com/
Any comments on it would be good. Thanks for listening!