The Tecnu soaps and the IvyBlock creams do work, but they are expensive. Instead of Tecnu soap (originally developed as a skin cleaner in the event of a nuclear blast!) try plain old rubbing alcohol. It's a solvent for urushiol, the oil that causes the reaction. It's a ton cheaper, and it works great. The only gotcha is that you have to wash fairly quickly with it, because urushiol binds to the proteins in your skin within a hour or so, and after that, no amount of washing is going to fix the damage. The IvyBlock cream is just a quaternium-18 bentonite based cream (it's like a clay, is also found is some womens beauty creams, and much cheaper), and it just provides a thin "skin" that blocks your skin from the oil.
As a friend told me one "with the best medical treatments in the world, poison ivy can be cured in 2 weeks, otherwise you have to wait 14 days". Corticosteriod shots makes you feel better, but don't stop the reaction.
You also need to wash, wash, wash everything that even might have come in contact with the plant, otherwise you'll just end up getting it again.
I had to clear an enormous amount of the stuff from a couple acres I have south of Houston. I had plants that went up in to trees 50 feet or more, with vines the size of my ankles (used a bowsaw to cut them). I bundled myself up like a lunar explorer, and ripped and cut it out, using Roundup (which works great).
One tip - don't rip vines out of the ground, use Roundup on them. I felt so self-satisfied ripping vines out (and then running home to wash), until the next spring, when each vine I ripped out now generated 150 little new vines, each one growing from each broken root. It was my worst nightmare, but Roundup came to the rescue.