- Newsroom (Robertson Blvd. in Beverly Hills, all ages)
They have hosted the L.A. Slashdot Meetup before, so they might be a good option. - The Well (Sunset/Vine in Hollywood, 21+)
Fairly spacious bar with plenty of seating on weeknights. - The Bourgeois Pig (Franklin/Bronson in Hollywood, all ages)
Cafe with back room that has hosted poetry readings in the past. - Philippe's (Chinatown, downtown L.A., all ages)
1001 N. Alameda St. Los Angeles CA. 90012 (across the street from Union Station)
They can seat 300 people, and have given us permission to place signage and use as much space as we need. Their upstairs area tends to be quieter. Downsides: They are only open until 10:00pm. (When the 2600 Magazine people use this place for their meetings, they just move the meeting to the nearby Denny's at 10:00). - Fred 62 (Silverlake, all ages)
It's a diner where the price of most things ends in .62. Booths made out of old car seats. Serves beer and wine. - Swinger's (West Hollywood)
Quintessential Hollywood diner. Cow patterned walls. Seating indoors or out. Beer, wine, and "smart" drinks (assuming there is anything "smart" about spending $7 on a tea-flavored smoothie). - Pete's Cafe (Downtown - 4th & Main by Skid Row)
Upscale; good food, full bar, beautiful old bank building - How about Caramba Restaurant just for self-referential goodness.
(to add your own suggestions, edit the list of locations page)