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

Tasker - Tasker is an application for Android which performs Tasks (sets of Actions) based on Contexts...

Answerbase - Add a Q&A system to your website in just minutes, with Answerbase's powerful question and answer software for online communities and customer support.

Automate - Automate various tasks on your Android smartphone or tablet.

utterances - A lightweight comments widget built on GitHub issues.

Locale - Locale helps content owners and translators work together, so Rails developers are free to write more code