DISQUS - Disqus is a global comment system that improves discussion on websites and connects conversations across the web.
Mobilize - Mobilize is a scalable messaging app built for large groups.
IntenseDebate - IntenseDebate's comment system enhances and encourages conversation on your blog or website.
Crowded Communities - The all-in-one community platform.
Commentbox - Commentbox is a jsf component that allows quick realization of a comment functionality
NationBuilder - The world's first platform for leaders, handcrafted from scratch to help you grow your community and lead them to action.