A number of organizations are dedicated to those who share a passion for building sailplanes at home from scratch or from available plans and kits.
This is amazing: in searching for information to post here, I find that my old friend and roommate from about 1985, Roy Bailets is now developing an ultralight rigid-wing hang glider using advanced composite technology. Roy had started working with Burt Rutan on the Voyager non-stop around-the-world aircraft in the mid-80's and has since started his own composites fabrication company in Mohave, CA.
The Raptor hang glider he is manufacturing is designed by Matt Kollman and you can find aircraft specifications and a first-hand report of its maiden and subsequent test flights here: https://www.delta-club-82.com/bible/293-hang-glider-raptor.htm.
Websites with information on homebuilt sailplanes:
Experimental Soaring Association https://esoaring.org
Formerly Sailplane Homebuilders Association
Holds an annual meet at the gliderport in Tehachapi CA on Labor Day weekend.
A fairly complete listing of web sites and information
Australian Homebuilt Sailplane Association
Foot Launched German Sailplane
Building the HP-18
Marske Flying Wings
Briegleb 12/16 N7438 Sailplane Restoration
List of available sites, plans, kits, parts, engines, projects and associations
Webring on Homebuilt Sailplanes