So I was playing with the shake effect in Script.aculo.us (an AJAX library). It will shake back-and-forth when you enter a bad password (like in OS X).
Anyway, click on my blue tie (up above) or here for a little surprise.
Adding all that AJAX and Adsense slows down my site a little bit, sorry.
Update 2021-01-02: I removed this effect back in 2006, but I kept this post. Funny to see how excited I was about a little JavaScript visual effect.