I am looking for players to join a play-by-chat game. I have set up a wiki for the game at Obsidian Portal, and have advertised on a couple Yahoo Groups dedicated to gaming. Are there any other places to advertise that would get some good results? Thanks!
I'd recommend finding a forum devoted to the specific type of game you want to run. The smaller and more narrow, the better, as such forums are more likely to a) be inhabited by the players you want to reach, and b) self-police. If you were looking for an OD&D game, for instance, you might check the OD&D Discussion Boards rather than rpg.net. Big, broad forums are inhabited by a distressing number of lunatics.
If that's not an option, perhaps because there's no forum devoted to the type of game you want to run, or because your system is so popular that most forums devoted to it are quite populous (such as D&D 3.x or 4e), I'd highly recommend being very, very specific about your playstyle and what you're looking for out of players. No matter how many or how few people respond, don't say "you're in" or anything specific until you've corresponded with them a bit. Just let them know they're on the list and you'll get back to them, then politely turn down anyone who squicks you out or seems incompatible. No need to get specific, just thank them for their interest and move on. You will encounter some bizarre people in online gaming and nothing sinks a game faster than incompatible or disruptive players.
http://www.meetup.com is a great place
Enworld has a new section called Gamers Seeking Gamers. They have lots of users and lots of interested people there. Plus they cater to all kinds of RPGs.
http://www.gamersgather.com is somewhat in beta mode right now, but in talking to the site owner it seems really promising.
What sort of game do you want to play? Most companies have some sort of forum site you could use to advertise playing their game. You might also try related sites. For instance, if you want to run a game based on anime, you might try anime forums.
You might also want to look at the big sites, places like RPG.net and similar.
Best of luck!
One successful site is warhorn.net.
I'm a fan of Obsidian Portal myself.