Linkello - Video calls simplified, no installation required.
Pluot Communications - Big-screen video conferencing for startups
jTorchat - jTorchat stands for Java Torchat, and is a complete rewrite of the popular p2p IM messenger Torchat
Team.video - Happier, more productive video meetings
Signal - Fast, simple & secure messaging. Privacy that fits in your pocket.
Slack - A messaging app for teams who see through the Earth!