CloudFone is a SIP-Softphone. It has unique features that make it difference from other softphones.
SIP standards Protocol
Call Conferencing (up to 5 lines)
Can play pre-recorded voice greeting after call connected
Call Recording (Voice and Screen Record)
Web Browser Integration for web-app like CRM (SRWare Iron Web browser)
SipBuddy for call-center agent training/observation
And many more features
FREE for non-commercial use.
Supports Windows Vista, Windows 7 and Windows 8