Linkello - Video calls simplified, no installation required.
Whereby (formerly appear.in) - Collaborate from anywhere - video meetings with no downloads
jTorchat - jTorchat stands for Java Torchat, and is a complete rewrite of the popular p2p IM messenger Torchat
Brie.fi/ng - Start secure group video chat
Signal - Fast, simple & secure messaging. Privacy that fits in your pocket.
MeetSpace - Video conferencing for teams that doesn't suck