Amsat
Amateur Satellite organization.
This international organization coordinates Radio Amateurs as volunteers to design and build the OSCAR series of radio ham satellites (OSCAR = Orbital Satellites for Communications by Amateur Radio).
The OSCAR program has been highly successful. Several OSCAR satellites have been launched as stand-by payloads on commercial or government launch vehicles.
Under international treaties, they are allowed to use radio frequencies reserved for licensed radio amateurs.
Web site: AMSAT Web Site.