The Asterisk app_rpt Project - Using open-source Asterisk PBX and Linux to build an internet linking platform to simultaneously control several repeaters at one site. Technical and contact information. - http://zapatatelephony.org/app_rpt.html
EchoLink - System to connect amateur radio operators to repeaters, simplex links, and other hams. Includes interface information, documentation, and node information. - http://www.echolink.org
Internet Radio Linking Project (IRLP) - High-end project to link repeaters worldwide via the Internet. Includes node status, hardware and linking information, and FAQ. - http://www.irlp.net