First and foremost, I cannot take credit for this incredibly cool hint. I was searching Google for something completely unrelated and when the words SmackBook Pro appeared in the search results, I just couldn't resist clicking and having a look.
In summary, some very clever person has found a way to maintain muliple simultaneous desktops on their MacBook Pro (using Desktop Manager) and switch between them by ... yep, you've guessed it, gently smacking the side of the screen. More information on how to set this up, and a video of a 'SmackBook' in action, can be found at the above link.
[robg adds: This came out earlier this year, but I didn't think to run it as a hint. The above link provides detailed instructions on exactly what you need to do, as well as a set of downloadable code snippets to make it happen. I haven't tested it myself, and don't have any plans to do so...but the video is fairly interesting to watch.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20061210094359719