I had to hurry with the camera, for fear it'd get away, so these shots aren't very good, but here it is a little closer:
Yep, it's a woodchuck. It was probably about to eat the blooms off the wild violets in front of the house, which they really seem to like a lot. Every year when those flowers disappear, I figure there's a woodchuck around somewhere.
Incidentally, I did manage to get an Easy-Macro shot of a violet before the woodchuck got to it!