Falcon Science Fiction and Fantasy Society: Promoting science fiction and fantasy in Nova Scotia through game cons, writing contests, artwork, costumes.
Gaming Convention Listings by Jenga: One of the most complete game convention listing sites, with good searches.
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.
RPG Registry: Huge database of role-playing Conventions, players, and games - both online and offline.
RPGA Convention Calendar: Webpage goes to current month of official RPGA activities in the United States.
Steve Jackson Games - Convention and Trade Show Schedule: Listing of events submitted to Steve Jackson's list, from all over the world.
The ConMen Syndicate: Gaming e-zine and convention listings from around the globe.
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.
The SF Site: Conventions: Science-Fiction gaming convention calendar.
UK RPG Convention Calendar: Upcoming roleplaying games conventions in the British Isles. Looks comprehensive and informative.