I just clicked randomly in the top right corner of a bucket of windows and something funny happened: the address bar and navigation bars disappeared and the content part of the window took over. It was rather nice. Check it out:
Here's the before, with all Navigation Toolbar (where the Address box and Search boxes are), the Bookmarks Toolbar, and even the Web Developer's Toolbar.
Click that little button in the top right corner, and poof, they all disappear, giving you much more space for the Web site you're looking at (or taking screenshots of, or whatever):