HelpNDoc - What is HelpNDoc ? Easy to use yet powerful help authoring environment which can generate various documentation formats from a single source.
Freshservice - Freshservice: the one-stop cloud solution for all your IT management needs.
Dr.Explain - Dr.Explain software is a help file authoring tool.
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
CHM Editor - Best solution to edit CHM files
Zendesk - Zendesk is a beautiful, lightweight help-desk solution.