Some friends host a games night, which I expect nets them a good number of testers.

You could also just go to a coffee shop. The pitch I'd try: "Hey, I'm making a game. If you try it for 5 minutes, I'll buy you another drink." If people keep playing beyond the minimum, you know you're getting somewhere.

Personally, I wouldn't use IRC much, because then I can't watch people in action. I don't make games, but I regularly watch people using software I've made. Their words may lie, but their expressions and actions usually tell the truth.

You might also have people try a few games, with only one of them being yours. People like to please, so you can just say, "Hey, I'm doing some market research on video games; would you try these?" If they don't know which one is yours, you may get much better answers.

Coffeeshop, Craigslist posting, take it to local game events (IGDA meetings/etc), contact local game schools and bring it there for testing (game schools are everywhere)...

The TIGSource forums (forums.tigsource.com) are a good place to get feedback online, and has sub forums dedicated to both playtesting and devlogs. Quite a few well known indie games (Minecraft, Fez, Cube World, Papers Please) first appeared on the TIGSource forums.

Depends entirely on the project, of course. But putting up demos, preferably as web pages, if that's not possible as a binary, tends to be a great way to show the world what you're doing. Open-source of course makes it easier (just throw it on github). Subreddits, irc, HN, and forums make great channels to get people to look at something. Another good approach, but that only works if you're near a big population center, is to find a relevant user group and do a talk there.

Depends on the technology you're using, for Flash Newgrounds is a great resource, even the worst game normally gets tried 500 times.

4chan.org/v/