I recently downloaded an open source animation program called Pencil. I like it so far, aside from some little quirks with the interface. It has been incredibly useful for roughing out my animation a bit more, and the result of an hour or so of messing with it is this:
Still very early. I still need to touch up the timing a bit (it's a little too consistent, needs to look more natural) and then polish it up with more appealing art but... it's a huge improvement over the way I had been animating before. I was just drawing layers in GIMP and hoping they looked okay when I exported as a GIF.