Swallow Hill is a good place to start for music in Denver. (www.swallowhill.com) And yep, Harry Tuft is still doing the Hootenannies. Bless his heart. The next one is Dec. 6th.
There are gospel/bluegrass jams at the White Fence Farm. (whitefencefarm.com) on Thursdays I think. More info on such things can be found by my friends, Bing and Suzie on their Gospel Grass website. (www.gospelgrass.com).
There are some open stages in the foothills in Evergreen, Indian Hills and Aspen Park if you want to travel further. Holler and I'll post more details.