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.

Bloomfire - Let Bloomfire help you get organized! Organize your content, build your company knowledge base and help your employees to be more successful.

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

Confluence - Confluence is content collaboration software that changes how modern teams work

Zendesk - Zendesk is a beautiful, lightweight help-desk solution.

Tettra - Tettra is a company wiki that helps teams manage and share organizational knowledge.