Microsoft HTML Help - Microsoft HTML Help is the standard help system for the Windows platform.
xchm - xCHM is a cross-platform GUI front-end to chmlib, with borrowed bits from Pabs' chmdeco project.
ExtraCHM - A fully featured reader for Compiled HTML (chm) documents.
Chmox - Chmox is a free (of charge), open source application for OS X which lets you read Windows Help...
Read CHM - Read CHM is ultimate CHM (Compiled HTML Help) file reader.
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.