If you see Facebook as a benevolent time-waster, why not waste your time more efficiently when you’re there? Hit Alt+1 for the home page, Alt+? to search, or Alt+M for a new message.
The How-To Geek runs down all the shortcuts he’s discovered. Aside from Alt+M and Alt+?, most of Facebook’s keyboard shortcuts line up with numbers. 1-5 will take you (roughly) from left-to-right on Facebook’s navigation links across the top of your Facebook page. 6-0 will navigate to less obvious settings pages.
NOTE: If you’re on a Mac, you (currently) need to add Ctrl+Option+ to each of the shortcuts (Firefox on Mac is Function+Ctrl—thanks Robert Reents!). Other than that, they should work the same.
The Geek notes, however, that the shortcuts work best in Chrome, and maybe Opera and Safari. In Firefox, you’ll need to add a Shift key to the combination, so as not to trigger Firefox’s own Alt-centered operations. On Internet Explorer, you’ll have to press Enter after hitting each combination.