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.
IntenseDebate - IntenseDebate's comment system enhances and encourages conversation on your blog or website.
Commentbox - Commentbox is a jsf component that allows quick realization of a comment functionality
Vuukle - Vuukle is a multi-point user engagement platform.
Hyvor Talk - The Best Commenting Platform For Your Website