Doxygen - Generate documentation from source code
CHM Editor - Best solution to edit CHM files
Slate API Docs Generator - Create beautiful, intelligent, responsive API documentation.
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.
FastHelp - FastHelp is a Windows Help File Generator that produces online and offline documentation.
Microsoft HTML Help - Microsoft HTML Help is the standard help system for the Windows platform.