Banjo Ben: Ben Clark has built a music teaching empire focused on Bluegrass music. There's tons of Tablature of bluegrass songs and fiddle tunes, for Guitar, Mandolin, and the Five-String Banjo. Subscription based, but there's tons of free resources! I'm a Gold Pick Member. :-)
Flatpicking Guitar: Dan Miller is a prolific multi-instrumentalist and longtime mastermind behind Flatpicking Guitar Magazine. He has written dozens of books on guitar instruction, and his books are among the most thorough I've encountered. (I own several of his books, and find them really useful!)
Musical U: This website is headed by a great music educator named Christopher Sutton. It's an outstanding resource for all things related to Music Theory, including ear training, scales, chord building, the Circle of Fifths, and more! It's subscription based, but there's tons of free resources!
Music With Ryan: Ryan Kimm has TONS of beautiful licks and bluegrass song arrangements for guitar! His site is one of the coolest that I've come across in a long time. Lots of free material, and reasonable monthly rates for his premiere memberships. Definitely worth checking out- I'm a subscriber!
Recommended Guitar Resources