I was browsing around for VOIP software and one of my searches led me here.. I can see lot’s of people don’t know what software is available..
Well I have been using Speakfreely for over a year now and it works.. It’s open source, versions for windows and linux are available (including other platforms). It’s very configurable and has so many features. Give it a try:
http://www.speakfreely.org (windows version)
http://www.fourmilab.ch/speakfree/unix (*nix version