This squirrel rig is a nice cartoony rig that can be used for some fun character animation. It was created by the very talented Josh Burton and
can be downloaded for free at Creative Crash.
The only tricky part about animating with the Squirrely rig is the enormous tail - which is almost a character in itself.
Lots of your time will be spend doing overlapping action and follow-through, to make the tail feel natural.
Still, what did you expect - a squirrel with no tail?