The Macbook ships with a remote control that allows you to control Front Row and a couple of Apple's applications like itunes, quicktime, dvd-player and the system-volume.
Beyond that, you can't do much else with it, though.
With Remote Buddy you can do way more that just that.
It gives you control over the rest of your computer via the remote control (or even a wii remote) and also improves the available functionality in those apps that already supported the remote control by themselves.

You can download a trial version right here.

Feel free to dump your own Macbook tips in the comments!