OpenSER
A branch of the SIP Express Router project, offering an open-source SIP server. 3CX
Developers of IP PBX software for Windows. Applied Voice & Speech Technologies, Inc. (AVST)
Applied Voice and Speech Technologies, Inc. (AVST) offers SIP integrations to its flagship CallXpress unified communications platform. BaseVoice
Commercial software development company that produces PBX, router, proxy and application server software. Bluenote Internet Telephony Networks
Server software targetted at the enterprise sector. Interactive Intelligence, Inc.
Developers of a proxy server. Site contains downloads, documentation and a forum. LignUp Corp
Applications developer. Products include software PBX's for enterprise and service providers.