QuHelp is a command-line program that scans a directory with HTML formatted text files and builds a help site using that directory's content and a template. A default template is included, but any template can be specified. QuHelp adds a nice expandable tree view of the help site's contents, a navigator, permalinks, and other useful stuff for browsing the help site.
The wiki has become the clear choice for use among projects for their help documentation. Wiki Web Help takes the wiki concept and tailors it for use specifically with help documentation. It combines the best of both worlds, with operation similar to a chm viewer and the Web technologies that enable community involvement. It features a dual split pane with tabs for searching, index browsing, and display of contents (in a tree). Users can create and modify topics and pages. Pages can be tagged for index creation. Searching with highlighting is included.