Guild of American Luthiers 
A non-profit educational membership organization, formed to advance the craft of string instrument making and repair. Includes details of membership, events and of their quarterly magazine.
http://www.luth.org/Luthiers Interactive of North Texas (LINT) 
A group of luthiers and repair people who meet every two months. Offer articles, tips, a gallery and meeting notes.
http://www.lint.org/
North California Association of Luthiers 
Information about meetings and membership.
http://www.frets.com/NCAL/
Southern California Association of Luthiers 
Information about meetings, membership, and their magazine; also offer a collection of articles on lutherie.
http://www.guitarbuilder.org/
Seattle Luthiers' Group 
An informal group of stringed-instrument builders in the Seattle area, meeting to share experience and skills. Includes schedule and members directory. [US]
http://www.seattleluthiers.org/