Leaves of Three, Let it Be: The one thing that doesn't vary is the pattern of three leaflets branching from a single, independent stem. Two leaves are attached directly to the stalk opposite each other. The third leaf juts out from them at a right angle, so the 3-leaf pattern forms a triangle. There are no additional leaves on the same stalk.
The leaves may be serrated, round, or oak-like depending on what other foliage is around the poison oak plants. They may be shiny, or not. They may have a red tinge, or not. Be wary, or you're in for a week of itchy torture.
The plant itself may be single stalks of three leaves close to the ground. Or a bush. Or a vine climbing up a tree. Most photos were taken on one trail in the Columbia Gorge.