Here are my picks, as well as some sources for the material heard on my showroot:

Contemporary Record Labels Featuring Roots:

• Old Hat Records - Based in Raleigh, NC, focusing on Southern folk music
• Times Square Records
• Roots and Rhythm
• Smithsonian Folkways Records
• Yazoo Records
• ProperMusic.com - Proper Records, a British label keeping the American roots alive
• Archeophone Records
• JSP Records - another British label reissuing American jazz and blues
• Arhoolie Records - reissue label specializing in cajun/zydeco and old-time country
• Bear Family Records - German reissue label that really digs deep into the blues, country and calypso.

Free downloadable music (mp3):

• Turtle's 78 RPM Jukebox
• The Doo Wop Jukebox
• Internet Archive: 78 RPMs
• The UCSB Cylinder Digitization Project: Hundreds of original Edison cylinder recordings from 1898 to 1925.
• American Memories (The Library of Congress): Several audio recordings available.
• Public Domain 4U: AWESOME public domain blues, jazz and country from the 1920s & 1930s.
• Old Phonograph Records
• The Roots Music Listening Program: Perhaps the most complete free roots collection on the Net

Podcasts and Internet stations:

• Radio Dismuke: Live365.com channel featuring 20s & 30s jazz & pop.
• Doo Wop Cafe Radio: Featuring a plethora of DJs who really know their stuff.
• DKOS Media: Home of "A Different Kind of Oldies Show"
• Bob Dylan's Theme Time Radio Hour: An American icon who plays incredibly cool, rare roots music.
• The Antique Phonograph Music Program: Podcasted radio show featuring recordings from the Acoustic Era (pre-1930) played on vintage equipment.  Heard in the New York City metro area on WFMU 91.5 FM.
• The Lost Discs Radio Show: Heard on WBCQ shortwave frequencies 7.415 & 5.110 MHz and on podcast, featuring rare 45s from the 50s & 60s.

Broadcast radio stations and shows:

• WHVW AM 950 Hyde Park/Poughkeepsie, NY: Perhaps the best all-Americana station in existence.  Specializing in hillbilly, western swing, blues, R&B and doo wop.  Worth going out of your way to hear while in upstate NY, until they start Webcasting.
• WPAQ-AM 740 Mount Airy, NC: A locally-owned AM station in the Southern tradition, featuring gospel, bluegrass and old-time country, with some 30s & 40s pop.  Can be heard in the Triad with a good radio.
• American Routes: Syndicated public radio program from New Orleans.
• Back Porch Music: Featuring bluegrass, folk and blues from past and present.  Heard in Greensboro on WUNC 91.5 FM
• WQFS Blues Show: Hosted by my friend Mike Caudle, heard Thursdays from 2 to 4 PM.
• Let the Good Times Roll: Immediately preceding my show, Fridays from 8 to 10 AM, with Wild Bill Clubb.
• Let the Good Times Roll: Not to be confused with Wild Bill's show, a syndicated public radio program heard locally on WNAA 90.1 FM on Saturdays from 6 to 8 PM.