Juvia - A commenting server similar to Disqus and IntenseDebate
Master Comments System - Master Comments System is a very compact comments system with basic options:
IntenseDebate - IntenseDebate's comment system enhances and encourages conversation on your blog or website.
talkatv - talkatv is an open source comment service much like ...
Remarkbox - Remarkbox offers a free comment system to keep readers engaged with your content.
DISQUS - Disqus is a global comment system that improves discussion on websites and connects conversations across the web.