UPDATE: In January 2004, SEGA did a revamp of their site. As such, most of my links to sega.com no longer work.
Unofficial Sega message boards
http://www.dxbnet.net/segaforums/
Sega's Official Phantasy Star Online Site
http://www.sega.com/pso - not working
Sega's Online Help Page
http://www.sega.com/help/online/online.jhtml - not working
Sega's PSO FAQ
http://score.sega.com/games/phantasystaronline/help/index.html
History of Phantasy Star
http://www.sega.com/segascream/legacy/historyofpso.jhtml - not working
Sega's Message Boards
http://boards.sega.com/cgi-bin/segaboards/ikonboard.cgi - not working
My Profile on Sega's Boards
http://boards.sega.com/cgi-bin/segaboards/profile.cgi?action=show&member=gemini1978 - not working
A different Sega PSO Message Board (appears to be a GameCube board)
http://boards.sega.com/cgi-bin/pso/ikonboard.cgi - not working
Sonic Team's Official Page
http://www.sonicteam.com/
Planetweb (Dreamcast Web Browser)
http://dreamcast.planetweb.com/
game player s (old site)
http://www.geocities.com/game_player_s/index.html
game player s (old site #2)
http://www.geocities.com/psoarchive/index.html
game player s (new site)
http://rodenta1031.myftp.org/psoarchive/
GameFAQs Phantasy Star Online Message Board
http://cgi.gamefaqs.com/boards/gentopic.asp?board=26576
GameFAQs Phantasy Star Online Version 2 Message Board
http://cgi.gamefaqs.com/boards/gentopic.asp?board=31602
IGN - Phantasy Star Online
http://dreamcast.ign.com/objects/013/013022.html
IGN - Phantasy Star Online Version 2
http://dreamcast.ign.com/objects/016/016431.html
PSO World
http://www.planetdreamcast.com/psoworld/
PSO Quest
http://www.psoquest.com/
Camineet - Phantasy Star Online
http://www.camineet.net/
Green Hill Zone - Phantasy Star Online
http://www.emulationzone.org/fanfare/ghz/pso/index.html
Phantasy Star Net
http://www.phantasy-star.net/pso/pso.html
Sonic Stadium - Phantasy Star Online
http://www.sonicstadium.org/games/dc/pso/
PSO Central
http://www.freewebs.com/psocentral/
Planet PSO
http://www.planetpso.com/planetpso/home/
Phantasy Star Online FAQ #1
http://dimensions.sega.free.fr/
Fuzed - Phantasy Star Online PC Version
http://www.fuzed1.com/psopc1/01/