The RPG Consortium
RPG online community with discussion forums for different games and gaming styles. Includes archives of publications and reference materials.
http://www.rpgconsortium.com/

RPGMP3.com
Audio resources for roleplaying sessions, as well as audio reviews and downloads.
http://www.rpgmp3.com/

Magister Ludi Roleplaying Resources
A collection of articles about GMing, with practical tips and advice, and a collection of roleplaying related links.
http://users.chariot.net.au/~amaranth/articles.htm

RPG Cliches
A list of cliches and absurdities that occur in traditional RPGs and LARPs – either in the books themselves or in the actual playing of them.
http://atrocities.primaryerror.net/rpgcliches.html

Strolen's Citadel - The Idea Guild
Searchable fantasy resource for game masters and players for original plots and items.
http://www.strolen.com/

Random Dialogue: Gamemastering
Includes tips for Game Masters, a thesis on running Shadowrun games, and detailed campaign journals.
http://www.randomdialogue.net/gaming/gming.php

Palladium Books Reference
Listing of the products Palladium has published, with cover scans, ISBN numbers, cover prices, and print status.
http://www.oddworldz.com/1010101/index.html

RPG Portal from Japan
Information about tabeltop roleplaying in Japan.
http://www.trpg.net/en/

RPG Tips
Tips, forums, and general information.
http://rpg_tips.tripod.com

Styles of Roleplaying
John H. Kim's rec.games.frp.advocacy FAQ, dealing with abstract (no one system) and RPG classification issues.
http://www.darkshire.net/~jhkim/rpg/theory/