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."
FBBT (Free Bluegrass Backing Tracks) - www.fbbts.com/Home.html The backing tracks hosted are Simon Mitchinson personal collection and are completely free and available to help with your practice. Each link on the tunes pages will play a chord progression in the style of the song in the title. If there is a song or tune that you would like a practice track for, suggest it to Simon (email address in the "About" tab).
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."
Idaho Bluegrass Music Camp - for banjo, guitar, fiddle, and mandolin -https://www.idahobluegrasscamp.org/ This is a four day workshop at the beginning of June in Weiser , ID with nationally known instructors and limited to 15 students per instructor. More info on the web page.
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.
Tintype Portraits of Old-Time Musicians from Appalachia - https://nyti.ms/2CHKH9g Traveling around Appalachia in her mobile dark room, Lisa Elmaleh chronicles the people preserving an unglamorous American tradition.(New York Times article)
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