Additional Resources
MusicTheory.net
A free website that provides lessons, exercises, and tools that help develop your understanding of theory and ear training.
Forrest Guitar Ensembles
Andrew Forrest has a website that provides free arrangements and compositons for solo guitar, duet, trio, quartet, orchestra and so much more. Great for all levels!
IMSLP
Petrucci Music Library contains over 600,000 scores that are in the public domain. You can find anything from Sor, Carulli, Giuliani, Mertz, Villa Lobos. If it's in the public domain you can most likely find it there.
Please feel free to let me know if you know of any other great sources for guitar or music education.
FingerTabs.com
They have tons of pop songs in classical and fingerstyle arrangments. Most tabs include sheet music and links to the performances by the arrangers. You might even see a few of my arrangements on there.