Having fought my own battles with woodchucks in my garden, I read Peter Rabbit Must Die in today's New York Times with great interest.
I was dismayed to discover one day last year that woodchucks had dug a tunnel which conveniently exited in the middle of the main garden bed in our yard. A number of plants were destroyed, including a unique liatris I've only recently been able to replace. The woodchucks snacked on all sorts of plants, leaving us with far fewer vegetables (primarily beans) and flowers (primarily purple coneflower) than we'd have otherwise had.
I first tried filling the hole, but within a day the hole had been reopened. We then went the humane route; the company which mows our grass put out a havahart trap, the plan being that they would release anything we caught at a nearby nature preserve. We trapped a variety of animals - first a possum, then some skunks, then some woodchucks (pictures to come)! Things got quiet after that, but once there were signs of activity again this spring, I resorted to final sanctions: a package of The Giant Destroyer, and we haven't seen a sign of anyone since. Meanwhile, the garden flourishes.
Hot off the presses from the Blue Heron Farm blog: looks like we're not the only ones with a critter challenge - see Varmint Cong.
Update: here's a link to a subsequent post with pictures.