Linkello - Video calls simplified, no installation required.
Spike - Spike solves businesses' communication chaos by bringing together email, team chat, collaborative docs, and meetings, into one feed.
jTorchat - jTorchat stands for Java Torchat, and is a complete rewrite of the popular p2p IM messenger Torchat
Keybase Chat - End-to-end encrypted chat built into Keybase
Signal - Fast, simple & secure messaging. Privacy that fits in your pocket.
Crypho - End-to-end-encrypted messaging and file sharing