Mangler is an open source implementation of a client for connecting to
 Ventrilo 3.x servers. It supports keyboard and mouse button push to talk,
 GSM and Speex codecs, per-user volume control, a full featured server
 phonebook, the ability to connect to server without adding it to your
 phonebook, and native PulseAudio support.

http://www.mangler.org/

The Mangler development team resides on IRC on Freenode (irc.freenode.net:8001) in the #mangler channel.