Guitar
Wikipedia article describes the guitar family and its history; also links to related articles and external resources.
http://en.wikipedia.org/wiki/Guitar
The Guitar Pre-1650
The guitar and its predecessors: a small history.
http://www.whitetreeaz.com/guitar1650/
GuitarNation.com
A virtual gallery featuring a range of custom and hand-made guitars - nylon/steel string, acoustic/electric, archtop, bass, and historic recreations.
http://www.guitarnation.com/
GuitarSite.com
A resource for guitar enthusiasts. Includes newsletter, guitar history, interviews, tablature, directory, MP3s and chat.
http://www.guitarsite.com/
GuitarWiki
A resource for guitar players, to which everybody can contribute their knowledge. Includes history, information about the structure of the instrument, and tablature.
http://www.guitarwiki.com/
Harmony Database
For enthusiasts of Harmony guitars, a database of specifications and photos; includes acoustic and electric models, listed by model number, brand name and family.
http://demont.net/harmony/
How Stuff Works: Guitar
Graphic seven-part tutorial on how acoustic and electric guitars work; includes sounds and a page of related links.
http://www.howstuffworks.com/guitar.htm
Kokomo Music
Vintage guitar collection on display, as well as CD recordings of vintage guitars for sale.
http://www.kokomomusic.com/
MoMI
The virtual Museum of Musical Instruments focusses on old guitars showing collections and exhibitions with different themes.
http://www.themomi.org/
Vintage Guitars and Basses
Information and photos of instruments by major companies like Fender, Gibson and Rickenbacker, as well as many smaller brands.
http://www.vintageguitars.org.uk/
Vintage Guitars Info
A collector provides an illustrated guide to vintage guitars (acoustic, electric, resonator and steel). Includes related articles.
http://www.provide.net/~cfh/
VintAxe.com
Collection of some lesser known vintage guitars produced from the 1950's to the 1990's with catalog scans, pictures and a message board.
http://www.vintaxe.com/
Help build the largest human-edited directory on the web.