I just found this one Ahead's website. Thought I would post it.
The voice-over IP solution for your PC!
SIPPS is an extremely powerful software product that turns your PC into a multifunctional communication system. Thanks to its unique encryption technology you can telephone other SIPPS clients via the Internet - and in absolute privacy. SIPPS offers you just about all the features of a modern ISDN telephone. An integrated telephone answering machine with a remote inquiry feature is a standard feature, and of course calls can also be transferred to other parties. SIPPS lets you freely choose from a number of different user interfaces ('skins'), Custom ringing tones, a variety of answering machine messages, as well as Messenger support - and much more besides.
Try it out yourself - you will be convinced by the quality and reliability of SIPPS. SIPPS demo:
SIPPS is a new product from Ahead Software AG, which has become world famous thanks to the success of its "Nero Burning ROM" application.
Demo available starting 28.04.03