What's good for poison ivy and poison oak?

Steroids. These reactions represent a contact allergy, and can be quite severe. The affected area needs to be washed thoroughly, and topical steroid creams can be applied. You can start with 1% Hydrocortisone from the drug store, but a more potent prescription cream will probably be necessary. In severe cases, oral Prednisone my be required.
Wash it off. Most important is to wash the juice off your skin as soon as possible. Cool soaks or ice packs can help. Hydrocortisone cream or anti-itch products like calamine, itch-x, etc. May help. Beyond that you may need prescription medication.