Below is a listing of open source software having to do with Telephony. For a list of VoIP and business telephone providers please visit Voip-Info.org.
SAMs emulates a basic answering machine. It maintains a single voicemail box that automatically detects faxes and is remotely accessable with a password. Also enables remotely activating an Internet connection, and changing the greeting.
accounting module rlm_mq for FreeRADIUS to put accounting requests as messages into IBM MQSeries. One of the submodules puts selected fields from VoIP accounting request in XDR encoded format and might be used for VoIP accounting.