xCHM is a viewer for Compiled HTML Help (CHM) files. xCHM is a cross-platform GUI frontend to Jed Wing's CHMLIB.
Success stories of xCHM on Mac OS X have also been received, and apparently xCHM even works if compiled under the Cygwin environment in Windows.
xCHM can show the contents tree if one is available, print the displayed page, change fonts faces and size, work with bookmarks, do the usual history stunts (forward, back, home), provide a searchable index and seach for text in the whole book. The search is a fast B-tree search, based on the internal $FIftiMain file found inside indexed .chm archives, and it can be customized to search in content or just the topics' titles.