If youve ever bumped into a Microsoft Compiled HTML help file (the giveway is the .chm extension) and resorted to starting up a virtual machine in order to run an instance of Windows to view the file, theres a better waya chm viewer for Mac OS X.
Chmox is an open source application that displays chm files on Mac OS X. Viewing a file using chmox is as simple as downloading and extracting a dmg, pointing at a chm file and you are good to go.
Chmox is written in Cocoa (Objective-C) and uses both WebKit, and chmlib. If you are looking to dig a little deeper into how to work with chm files, Matthew Russottos site is also worth a visit. Matthew has included information on the chm file format, which you can find here.
A good way to learn more about how chmox works is to spend some time viewing the source files, which you can peruse on the chmox project at sourceforge.