Directories

Falcon Science Fiction and Fantasy Society
Promoting science fiction and fantasy in Nova Scotia through game cons, writing contests, artwork, costumes.
http://www.angelfire.com/hi/falconsociety/

The Gamers' Keep Calendar of Events
Home of the Concentric webring (gamecon). A well-maintained list, although there are quite a few non-gaming conventions in there, or conventions where gaming is a minor part of what's on offer.
http://members.tripod.com/~Fugli_Troll/Calendar/index.html

Gaming Convention Listings by Jenga
One of the most complete game convention listing sites, with good searches.
http://www.geocities.com/jengacons/

Rocky Mountain Benefit Gamers Association
Raises money for small, local charities in the Rocky Mountain region, typically by holding various events throughout the year, many of which are gaming (like board games and role-playing games, not gambling) related.
http://bengames.org/

RPG Registry
Huge database of role-playing Conventions, players, and games - both online and offline.
http://www.rpgregistry.com

RPGA Convention Calendar
Webpage goes to current month of official RPGA activities in the United States.
https://events.wizards.com/RPGAWeb/external/calendar.asp

The SF Site: Conventions
Science-Fiction gaming convention calendar.
http://www.sfsite.com/depts/cons01.htm

Steve Jackson Games - Convention and Trade Show Schedule
Listing of events submitted to Steve Jackson's list, from all over the world.
http://www.sjgames.com/con/index.html

UK RPG Convention Calendar
Upcoming roleplaying games conventions in the British Isles.
http://www.philm.demon.co.uk/RPGs/conventions.htm