DigitalChalk - Online Training Software and Learning Management System (LMS)
Linphone - Linphone is an internet phone or Voice Over IP phone (VoIP).
Workplace by Facebook - Connect everyone in your company and turn ideas into action.
Zoiper - Cross-platform VoIP softphone dialer for SIP and IAX systems
Onehub - Onehub helps businesses securely share and control files in the cloud.
Sipdroid - Free and open-source SIP/VoIP Client