statuspage - A simple self-hosted status page site with an API written in Django under the BSD license.
UserVoice - UserVoice integrates easy-to-use feedback, helpdesk, and knowledge base management tools in one platform that empowers users to speak and companies to understand.
YUNO - YUNO is a web data driven company focussed on solving customer challenges in web data discovery and extraction space.
Freshdesk - Freshdesk is a cloud-based customer support software that lets you support customers through traditional channels like phone and email, social channels like Facebook and Twitter, and your own branded community
Yonyx - Decision tree driven Interactive guides for customer service
Zendesk - Zendesk is a beautiful, lightweight help-desk solution.