Discourse - Discourse is an open source discussion platform built for the next decade of the Internet.
Freshservice - Freshservice: the one-stop cloud solution for all your IT management needs.
Forumbee - Forumbee offers community forums for discussions, feedback and Q&A.
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
Directly - Directly provides on-demand customer service apps.
Zendesk - Zendesk is a beautiful, lightweight help-desk solution.