The Unarchiver - Get the top application for archives on Mac. It's a RAR extractor, it allows you to unzip files, and works with dozens of other formats.
Kchmviewer - Kchmviewer is a free, open-source CHM (MS HTML help) and EPUB viewer for Unix, Mac and Windows...
zpaq - Incremental Journaling Backup Utility and Archiver
xchm - xCHM is a cross-platform GUI front-end to chmlib, with borrowed bits from Pabs' chmdeco project.
FreeArc - FreeArc is a free and open source file archiver developed by Bulat Ziganshin.
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.