Allscifi: J.R.R. Tolkien Spotlight: Discussion of Middle-earth mysteries.
Boards of Lorien: Discussion forum with a Lothlorien theme.
Entmoot: Discussions of center around Tolkien, Middle-earth, RPGs, and chat. [vBulletin]
Halls of Quenta: Lord of the Rings fan fiction community.
Ithilien: Home of the Loughborough High School Tolkien Society.
Linaewen: Reflective bulletin board to discuss Tolkien's books.
Lord of the Rings and Tolkien Things: Message board and chat room. [Gamers board, IRC Chat]
LOTR Forum: BBS to discuss the books and movies.
LOTR Forums: Community system dedicated to LOTR and Tolkien. Also has fan art and news.
Middle-Earth IRC Channel: A chat channel on EFnet for discussion and trivia. [IRC]
Minas Tirith: Discussion featuring the Library Council FAQs. [Ultimate Bulletin Board]
Rohan: Discussion board with quizzes and RPG.
The Argonath: Discussion board for Lord of the Rings fans. Includes the movies, books and role-playing.
The City of Arda: BBS system based in Tolkien's fictional City of Arda.
The Message Halls: Online Tolkien community for fans of J.R.R. Tolkien, the Lord Of The Rings and Middle-earth.
TheOneRing.net Barlimans: Community chat rooms and discussion boards. [RPGboard, IRC chat]
Tolkien and the Inklings Forum: Michael Martinez's discussion forum for scholarly debate on Middle-earth. [Ultimate Bulletin Board]
Tolkien's Readers List: Email-based discussion list about J.R.R. Tolkien and his works.
War of the Ring Forums: Provides a community for discussion about The Lord of the Rings and other works.
Yahoo! Groups: lordoftheringstrilogy: Photo collection, newsroom, links, and newsletter. [Yahoo!]