Coda is

click to enlarge
not a free Mac
HTML editor, but you can play with the trial version to see if it suits your needs. When you first start the program, it will load the contents of your hard drive in the left sidebar.
The interface is very easy to navigate, allowing you to create a wide variety of files besides HTML. The toolbar contains six submenus: Sites, Edit, Preview, CSS, Terminal, and Books. If you get stuck, Coda provides a detailed user manual and a Developer section on its website.
Source: Coda