Bluegrass College -http://www.bluegrasscollege.org/ The Bluegrass College offers free "online lessons from the masters of bluegrass for banjo, bass, dobro, fiddle, guitar and mandolin."
Homespun Tapes -https://www.homespun.com/ Homespun Tapes "features the largest catalog of music lessons on DVDs and CDs available anywhere. Our lessons are designed for learning players at all levels, from absolute beginners (including kids) to experienced professionals -- and everyone in between."
Native Ground Books & Music - http://nativeground.com/ Books and more from Wayne Erbsen with the initial goal to preserve and present Southern Appalachian music, but soon developed into a broader range of American folklore, with themes such as the Civil War, cowboys, outlaws, railroads, rural America and gospel.
This will always be under construction.... there are always more great links out there.... Let us know if you have one for us to post