DISQUS - Disqus is a global comment system that improves discussion on websites and connects conversations across the web.
SolidOpinion - SolidOpinion is a fun, new and dynamic commenting platform.
Geist.chat - Add feature-rich responsive comment sections to your website.
Commentbox - Commentbox is a jsf component that allows quick realization of a comment functionality
IntenseDebate - IntenseDebate's comment system enhances and encourages conversation on your blog or website.
Viafoura - Viafoura is an easy-to-integrate social monetization platform that enables your to better engage, understand and monetize your community.