Facebook Notifications is just what it sounds like, a little app that keeps you up to date with your Facebook world regardless of whether you're actually watching the page or not.
At installation (or in Preferences later) you can choose to have Facebook Notifications startup with your Mac, and all you'll see is a tiny blue 'F' on the status bar. Clicking this opens a drop down menu that shows your most recent notifications and messages.
There are also options to see your news feed, profile, compose a message and update your status. All but the last option will open your browser though - you can only write status updates, and even that doesn't include the enriched sharing features of the browser Facebook page.
To run Facebook Notifications properly, you have to have Growl installed, although as that's a more or less essential Mac installation that's not a problem!
Great for Facebook addicts, FaceBook Notifications means you'll never miss your friend's news while you're Mac's turned on.