BookWidgets - BookWidgets is an excellent application that let you create engaging exercises in minutes and easily share a varied variety of beautiful and fun activities with your classroom and others.

IntenseDebate - IntenseDebate's comment system enhances and encourages conversation on your blog or website.

Padlet - Visual boards for organizing anything.

DISQUS - Disqus is a global comment system that improves discussion on websites and connects conversations across the web.

Socrative - Socrative helps teachers engage the class with educational activities to measure and visualize...

GraphComment - Add modern discussion and social interactions to your website