DISQUS - Disqus is a global comment system that improves discussion on websites and connects conversations across the web.
Linkello - Video calls simplified, no installation required.
Realtidbits - Powering the Realtime Social Layer for Entertainment, Local Media and High Traffic Blogs.
jTorchat - jTorchat stands for Java Torchat, and is a complete rewrite of the popular p2p IM messenger Torchat
JustComments - Easy to set up, ad-free and reliable comment system
Signal - Fast, simple & secure messaging. Privacy that fits in your pocket.