Goats and llamas. They love to eat the stuff and they're immune to it. Don't pet one after it's been floundering in it, though. I've read about people who have got rid of it entirely on their properties by using movable electric fences and a bunch of goats.
Lol, The county here hires a guy to bring in his goats and fence to get rid of the poison Ivy in some of the parks. I would think it be cheaper to use a few college kids and spot spray with roundup.
Poison Ivy is actually a really cool plant, It can disguise itself to match it's surroundings. It will take on characteristics in it's leaves of the plants that grow around it but can always be identified because it will always have a unique "lobe" on at least one leaf, it may be subtle but it is there.
Here's a pretty good article on it but not the one I was looking for.
Link. Google images of Poison Ivy and you will be able to see how it disguises it's leaves.
Here's another good link.
Link. 
