DISQUS - Disqus is a global comment system that improves discussion on websites and connects conversations across the web.
CSE Classroom Manager - Technology for Education
Commento - A fast, bloat-free comments system to foster discussion on your website
NetSupport School - NetSupport School supports a teacher with a wealth of dedicated assessment, monitoring, collaboration and control features.
IntenseDebate - IntenseDebate's comment system enhances and encourages conversation on your blog or website.
Class Charts - Class Charts is super fast behaviour management software, creating school seating plans in seconds.