Firefox 4 (and betas) only: Most browsers offer a "Fullscreen Mode" but still rely on the same address bar, tabs and other mechanisms to get you around. Home Dash reconfigures Firefox for quick searching and browsing without any toolbar whatsoever.
How do you browse without anything but the page on your screen? A pop-in control panel, one you activate with either a faint Firefox logo in the upper-left corner, or by hitting Control-L (Command-L on Macs). The panel contains a combination URL/search bar, and a grid of 24 of your most-visited sites on the right. As you type in search terms or site names, those 24 buttons change to reflect matches from your bookmarks or history. It's a more visual representation of the kind of thing you're doing in Firefox AwesomeBar or Chrome OmniBox already.
Home Dash is a free add-on that requires the latest Firefox 4 beta (currently at 10). The upside is that it installs without requiring a restart.