I'm a big fan of The Dakota Tavern. I don't get there as often as I'd like but when I do it's always a great time.
Sunday and Wednesday nights are the best times to check out live music. The Beauties play on Sundays, and quite often you'll see other popular local musicians hop on stage to play a ditty or two with the band. White Whale Wednesdays offer up a serving of weekly featured While Whale Recording Artists - always a blast.
Don't forget the food! I've yet to try the Blue Grass Brunch (though I really want to) but I've indulged in their mac-n-cheese and let me just say, oh my. It's lovely.
Come for the bands, stay for the mac-n-cheese.