Here's an update to the very basic ball rig for Maya that I put up earlier this past year. The controls, mainly the squash control, have been tweaked to be easier to select. The geometry now sits on its own layer which can be un-referenced to apply a different shader. But the big update is the addition of a splineIK-driven tail which can be scaled and placed wherever you like.
Download it HERE, or by clicking on the image above. Enjoy!
Edit Feb 27, 2010: I've added an alternate .ma download for those who work in versions of Maya previous to 8.5. You'll need to edit the file in a text editor and replace all the lines that designate the Maya version (2009 in my case) with your version, or just delete that line completely. I have no way of testing this, btw, but it should work just fine.