DISQUS - Disqus is a global comment system that improves discussion on websites and connects conversations across the web.
MemberVault - MemberVault is a flexible platform that helps you to create, deliver, and sell your services, courses, memberships, subscriptions, etc.
IntenseDebate - IntenseDebate's comment system enhances and encourages conversation on your blog or website.
Ruzuku - Ridiculously easy online courses
Commentbox - Commentbox is a jsf component that allows quick realization of a comment functionality
Opentute - Opentute helps businesses to effortlessly launch a private eLearning and communication platform to engage teams and clients.