TetriNET

Blocktrix - http://strike.vectorstar.net/
Tetrinet client for Windows. Offers screenshots and forums.

Extreme TetriNET - http://campus.fortunecity.com/chemistry/933/tetrinet/
Home of Team Extreme. Downloads, server listing, game explanation.

G7 Software - http://www.g7software.net/
Creators of Tetrinet Aqua for OS X. Contains game news and downloads.

Planet TetriNET - http://tetrinet.emugaming.com/
Includes news, strategy, files, links and forum.

Pulper's TetriNET Site - http://www.geocities.com/TimesSquare/Alley/9430/
Contains themes, strategies, and downloads.

Raiden's TetriNET Themes - http://www.sonic.net/~raiden/tetrinet.htm
Contains about a dozen themes.

RedBox's TetriNET site - http://members.tripod.com/~TheTetriNET/
Downloads, themes, and an IP lister that doesn't work if you're on a LAN.

Slanter's TetriNET Emporium - http://www.geocities.com/MotorCity/Track/2525/tetrinet.html
Contains a few themes.

TetriNET - http://thor.prohosting.com/~ctail/tetrinet.htm
Contains general information about the game.

TetriNET Castle - http://www.geocities.com/TimesSquare/7785/tetrinet/
Includes information on ladder play, clans, downloads, and how to find players.

TetriNET Homepage for DALnet. - http://tetrinet.nols.com/
IRC channel #Tetrinet on DalNET's homepage. Teams, how-to's, and downloads.

Tetrinet Page - http://skyscraper.fortunecity.com/cern/676/tetrinet/tetrinet.htm
Includes game download and one custom theme.

TetrisZone: TetriNet - http://www.fortunecity.com/underworld/tetris/500/tetrinet.html
Screenshots, tips, themes, and links to other Tetris-like games.

The Tetrinet Site - http://www.geocities.com/tetrinet31/index.html
Downloads, themes, IP addresses, information guide, and links.