<animateTransform>elements to achieve the zooming hover effects.
Once I got that working, I felt like I really should make the icons do something useful when you click them. So, I hooked them up to control an embedded iframe.
Here's the result: SMIL Dock
(Note that the demo will only do anything useful in a mozilla-central nightly build -- that is, Firefox 3.7 / Gecko 1.9.3 -- since earlier versions don't have support for SMIL.)