The Soaring Society of America, or SSA, was formed in 1932 to foster and promote all phases of full-scale soaring or gliding. The SSA actively encourages involvement of youth in the sport (student pilots can fly solo at age 14!) and provides representation to Federal agencies to preserve glider access to airspace, much of it done on a volunteer basis. Through the FAST program, the curious can get an introductory lesson and flight time with an instructor for just $139.
You can also visit the website for the National Soaring Museum.