Office Software - Telephone

Ventrilo is the next evolutionary step of Voice over IP (VoIP) group communications software. Ventrilo is also the industry standard by which all others measure themselves as they attempt to imitate its features.

Make calls from your computer - free to other people on Skype and cheap to landlines and cell phones around the world.

The OpenWengo project's goal is to build Open-Source, community-driven software that addresses the shared needs of Voice Over IP users, by leveraging the many Open Source low-level components available today. The ubiquity of the Session Initiation Protocol, the need for a cross-platform communications system, and Free Software goodness are the cornerstones of the OpenWengo initiative.

Asterisk is the world’s leading open source telephony engine and tool kit. Offering flexibility unheard of in the world of proprietary communications, Asterisk empowers developers and integrators to create advanced communication solutions...for free.

Speak Freely is a 100% software-based VoIP phone originally written in 1991 by John Walker, founder of Autodesk. After April of 1996, he discontinued development on the program. Since then, several other VoIP "phones" have cropped up all over the world. However, most of these programs cost money. Most of them have poor sound quality, and don't support some of Speak Freely's basic features such as encryption, the answering machine, or selectable compression.