Express Talk VoIP Softphone

Express Talk is a free VoIP SIP based softphone for Mac OS X. it allows you to call other softphone users for free or normal telephones if you sign up to a SIP Gateway Service.
Features:
Configure up to 6 lines on the one phone with the ability to put calls on hold.

Supports caller ID display and logging. Includes a phone book with quick dial configuration. Can be configured to work behind NATs and Firewalls. Includes data compression (GSM, uLaw, ALaw, PCM and G726), echo cancellation, noise reduction, comfort noise and more. Uses the standard SIP protocol so it can use a number of telephone gateways, SIP systems or other internet phone software.
What's new in this version:
Version 4.04 may include unspecified updates, enhancements, or bug fixes.