Community Questions for Confluence - Keep questions and answers in one place with an engaging, community-driven Q&A discussion forum, powered by Confluence
Freshservice - Freshservice: the one-stop cloud solution for all your IT management needs.
Stack Overflow for Teams - Everything you love about Stack Overflow in a private 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
Question2Answer - A Q&A site helps an online community to share knowledge.
Zendesk - Zendesk is a beautiful, lightweight help-desk solution.