SJphone® is a VOIP softphone that allows you to speak with any other softphone running on a PC/PDA, any stand-alone IP-phone, or using Internet Telephony Service Provider (ITSP) with any traditional wired or mobile phone. It supports both SIP and H.323 standards and is fully inter-operable with most major VOIP vendors and ITSPs. Having SJphone installed is not enough to talk except over your local network. You have to obtain an account with any ITSP or SIP provider or install your own VoIP server.
… More
Edit
WHAT'S HOT
Simple, supports just about everything automatically
WHAT'S NOT
Ugly interface
THE FINAL WORD
Technically a brilliant product but not the prettiest interface around.