Guitarsite is a great resources for looking up contemporary artists such as Sharon Isbin, Julian Bream, John Williams and Marcos Vinicius.
Add Your Links, Free Directory, Link Submit, Free Link Exchange has a special focus on classical music.
The Online Guitar Directory is a guitar directory with useful links to guitar magazines and media.
Cleverjoe Guitar site with links to musical instruments, product information, guitar websites and guitar lessons.
Guitarnotes Guitar site with links to guitar instruction, tablature, mp3s and guitars.
Navaswan Guitar directory with links to discussion forums, sheet music and midi archives.
Click Dmoz Directory provides links to a range of musical sites.
in to catalog, publishes articles - some of which are relevant to guitar.List My Website is a human reviewed database that provides excellent search results.
Simple Submissions Web Directory provides links to great classical guitar lessons.