I'll second emusic.   There's Dock Boggs, Pete Seeger, The Duhks, Eliza Carthy, Steeleye Span, Fairport Convention, June Tabor, Martin Carthy, The Waifs, Dave Carter & Tracy Grammer, Dave Van Ronk, Richard Thompson (including 1000 Years Of Popular Music), Norman Blake, Neko Case, Tom Waits, Taj Mahal, M Ward, A. L. Lloyd, Be Good Tanyas, Steve Goodman, Karan Casey, Aoife Ni Fhearraigh, Anne Briggs, Shirley Collins, Mike Dowling, etc, etc