Have you hear of Folk Alley? It's a web site that streams folk music. My friends Phil and Cheryl had it playing one evening while I was at their house, and I liked it, and asked what it was. This evening I've just been enjoying the heck out of it. They play a wide variety including Celtic, and well, almost anyone you might hear on Prairie Home Companion. (OK, OK, I'm terrible at names.)
Anyway I'll include a link, so enjoy! Folk Alley is here.