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.
WinCHM - Creating CHM file, Make CHM file, Web Help. WinCHM Pro - Help authoring software (CHM, WebHelp, DOC, PDF) . With this powerful tool you can not only create chm file from scratch, but also convert a set of existing HTML files to a chm file.
Enchant - The easiest way to scale personalized customer support
Microsoft HTML Help - Microsoft HTML Help is the standard help system for the Windows platform.