Improv Encyclopedia
   Collection of improv games, drama exercises, improv handles, and references, indexed in 27 categories. Resources can be downloaded as a pdf booklet.
   http://www.humanpingpongball.com/

Improv Page, The
   Bernie Roehl presents a clearinghouse for information about improvisational theatre.
   http://www.improvcomedy.org/

International Playback Theatre Network (IPTN)
   Supports development of playback theatre worldwide through its programs and services, membership benefits, training resources, administration, and contacts.
   http://www.playbacknet.org/