For extremely cheap telephone service using VoIP, I have this device. Instead of having my computer on all the time, I have this box hooked up to my network. I then have a regular telephone plugged into it. Once configured, everything is magic.
I think I purchased mine from CanadaComputers - Cisco SPA122 on canadacomputers.com
I went through hell getting things working with my new VoIP.
It wasn't them, it was Linux and my system which were to blame.
Getting a phone number with voicemail and be able to make and receive local calls.
Trixbox enables even the novice user to quickly set up a voice over IP phone system. Trixbox can be configured to handle a single phone line for a home user, several lines for a small office, or several T1s for a million minute a month call center.
Supposed to support video conferencing.