Zoiper - Cross-platform VoIP softphone dialer for SIP and IAX systems
ClickMeeting - Collaborate with partners and clients using ClickMeeting professional web conferencing software. Try it now, FREE!
Sipdroid - Free and open-source SIP/VoIP Client
Zoom - Equip your team with tools designed to collaborate, connect, and engage with teammates and customers, no matter where you’re located, all in one platform.
Jitsi - Open-source video calling and chat platform.
BigBlueButton - Engage Your Online Students. BigBlueButton is a web conferencing system designed for online learning.