Yesterday afternoon, I checked in support for the <animateMotion> SVG element, so that feature is supported in this morning's nightly build!
The <animateMotion> element allows for much more flexibility in SVG animations. Mozilla's nightly builds have supported animation of most SVG attributes and properties for a while now, but <animateMotion> gives authors the added ability to effortlessly animate an element to move along any arbitrary path.
Marek Raida (a wizard of SVG demos, and the author of the "Cavern Fighter" game that I linked to a few posts back) has come up with two excellent <animateMotion> demos as well: "Drawing Animals" and "Catch the Mouse." Both are linked off of hist latest blog post. (Note: He's also got a fancier version of the "Catch the Mouse" demo where the mouse's footprints slowly disappear, but Firefox nightly builds are currently a bit choppy on that version, due to some code we should probably optimize for SMIL animation of CSS properties.)