Jewelweed (impatiens capensis) is known to relieve poison ivy irritation and other skin irritations. Crushing the stem releases fluid which can be rubbed onto the skin. http://customers.hbci.com/~wenonah/hydro/jewelwed.htm http://www.wildflower.org/plants/result.php?id_plant=IMCA
If you're near the ocean saltwater helps dry it out. Combine that with calamine, and just wait it out. I'm on the west coast and near a lot of poison oak. As soon as I even think I got exposed or my dog, cold water/dishsoap rinse straight away. Quarantine all clothes immediately.