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
Lessons With Marcel: Marcel Ardans is an AMAZING guitar picker with TONS of outstanding lessons on YouTube. He also gives Skype Lessons, and his teaching is among the best that I've seen. He's also BIG on music theory, so when you use a Fretboard Toolbox book with his videos, it's like he's reading from the pages. HIGHLY RECOMMENDED!!!
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. :-)