I just returned from Minneapolis-St.Paul recently, and while I was there I went to a nice folk session at Molly Quinn's. I don't have a lot of the information, but it was a Tuesday night. I'm sure there's someone here that might have more info.

I do know that there's a nice session on Wednesdays in Tempe, AZ (outside Phoenix) from 9 to midnightish...sometimes it's inside, depending on the weather.

The crowd is kinda young (average age is around 21, though they do let underagers in as well), and the music is mostly irish.