I enjoy all sorts of online discussion, but my favorite kind of electronic forum is the email mailing list. I'm a member in several lists run by others, and I also moderate a growing collection of my very own. All of my lists are "bad vibe free" and moderated to insure topicality and eliminate spam. Each has it's own guidelines for what's groovy to post; see the individual Yahoo pages.

• BlueRoom: The mailing list for people who like the Blue Room. Mostly, I use it to make odd announcements, post movie reviews and recipes, or otherwise fill your inbox with unexpected oddness. Not a discussion group, just a kind of surreal and cheerful experience.
• CGnD: The Cumberland Games & Diversions official mailing list. This one is for anything (Sparks, Points in Space, and so on) that isn't covered by the specific Fly From Evil or Risus lists. Not only do I announce new Cumberland news here, it's also an open forum for discoveries of any worthwhile paper toy/gaming eBook finds on the net, and a general Q&A forum. Moderated.
• Encounter Critical: The official mailing list for Encounter Critical, my roleplaying game from another past (an alternate 1979) where Planetary Apes and Amazons hob-nob with Hoblings in a fantasy world visited by the remnants of a war-torn galaxy. Garage-band RPG fun. Moderated discussion, fan-files and more.
• FlyFromEvil: The discussion forum for fans of Fly From Evil, my 1930s crime-drama RPG. Since the game isn't out yet, the list is understandably very quiet, but there's the occasional Q&A exchange!
• Mastery-Game: A discussion and games-seeking forum for Mastery players and users of Armin Sykes' excellent Mastery software for Windows.
• Pokethulhu-News: The official mailing list for players of the damned-odd-and-getting-damned-odder Pokethulhu Adventure Game from Squishy Brain Games, Dork Storm Publishing, and Cumberland Games & Diversions, in turn.
• Risus: An announcements feed (and articles/announcements forum) for fans of Risus: The Anything RPG, my brain-dead, freeware universal comedy (and other stuff) game. On the Risus list, I announce new Risus material, both my own and new fan-sites that have been spotted on the web. Fans are free to post their own announcements, and any Risus characters, variants, or articles they might cook up.
• Uresia: My mailing list for Uresia: Grave of Heaven, my slightly warped, darkly satiric fantasy world for Big Eyes, Small Mouth. Come share characters, ask questions, and see odd things!