Eight HTML samples (you can find them in directory samples/html) cover all features of the HTML sub-library.
Test demonstrates how to create wxHtmlWindow and also shows most supported HTML tags.
Widget shows how you can embed ordinary controls or windows within an HTML page. It also nicely explains how to write new tag handlers and extend the library to work with unsupported tags.
About may give you an idea how to write good-looking About boxes.
Zip demonstrates use of virtual file systems in wxHTML. The zip archives handler (ships with wxWidgets) allows you to access HTML pages stored in a compressed archive as if they were ordinary files.
Virtual is yet another virtual file systems demo. This one generates pages at run-time. You may find it useful if you need to display some reports in your application.
Printing explains use of wxHtmlEasyPrinting class which serves as as-simple-as-possible interface for printing HTML documents without much work. In fact, only few function calls are sufficient.
Help and Helpview are variations on displaying HTML help (compatible with MS HTML Help Workshop). Help shows how to embed wxHtmlHelpController in your application while Helpview is a simple tool that only pops up the help window and displays help books given at command line.