> Growl. It's not a Mac OS X builtin, but it's a must-install. I describe it to PC users this way: "Those little popups that Outlook does when you get new mail? Growl is a system-wide service that gives those to any application that wants them.

I wish Apple would just buy Growl or something and just build it in, the lack of a notification system in a modern OS was bizarre to me when I first realized it was missing. It's something that's missing in both OSX and iOS.