Ive used the Aveeno oatmeal bath to combat poison ivy.  I mix it up double strength in a Jar and apply it poultice style by soaking a clean cloth in it and applying it to the area.

Burt’s Bees also sells a poison ivy soap which is good for removing the oil and helping to dry out the area.

I would wash it with soap and then apply an aveeno poultice.

I used to get poison ivy terrible when I was younger… I swear all I had to do was look at the stuff and it would give me a rash :(