There aren’t a lot of free WYSIWYG editors out, and the ones that are available normally have terrible interfaces with limited functionality. I’m not a huge fan of WYSIWYG editors myself, but they can serve as a good starting point if you’re just learning how to code HTML.
The free Trellian WebPage app is nice because it makes use of the Microsoft Office-style Ribbon interface to provide an easy-to-use interface. As you’d expect from an app like this you can edit the content of a page through the WYSIWYG editor, the source code, or a split screen showing both. This program is also helpful if you are working with a free HTML template that you’ve downloaded, which are rather plentiful online.
The only thing I should mention is that when installing the program it tries to install an “SEO toolbar” on your computer, but uncheck the corresponding boxes or choose the “Compact Installation” option it will only install the app.
Trellian WebPage Homepage (Windows only; Freeweare)