I play at open microphone nights whenever it works out. Sometimes though I just watch (even if I was originally intending to play), because some folks that perform at some of these are really good musicians, and well, I’m a hacker. Just like I wouldn’t want to be the opposing starting pitcher against Justin Verlander, might not turn out so well.
Anyway, here’s a very useful website that lists all open mic nights across the country (including poetry and comedy), constantly updated, with links and other info. Pick a good one and you’ll be surprised at some of the talent out there, such as at this place for example.