Luthier Shaun Conrad started GuitarRepairBench.com to help inspire and educate people on guitar repair and building as well as to show off some of his own projects. The site has a comprehensive list of topics, an easy navigation system and excellent photos.
Guitar Man Acoustic Guitar Tips
Bob the "G-Man" has developed a site dedicated to the care and preservation of acoustic guitars. He has also started an Acoustic Guitarist Guild. Check out the "Best Guitar Tip of All"
Frank Ford's Frets.com Site
This site is published by Frank Ford, one of the most respected luthiers in the business. He has a fantastic website with extremely detailed information and great photos on the care and maintenance of acoustic instruments.
Bryan Kimsey's Lutherie Page
Bryan Kimsey is an active member of the Flatpick-L list group and a part-time luthier. Many members of the list send their instruments to him for repair and setup work. This page on his site explains his services and has some excellent reference material. Be sure to check out Bryan's sound clip page, too.
Stewart-MacDonald's Guitar Shop Supply
Stewart-MacDonald is the parts source for repair technicians, builders, and musicians since 1968