Turkey Tail, Trametes versicolor, is one of the most common mushrooms. It's also one of my favorites. I'm fond of many polypores, but what attracts me to this one is how it rewards close observation and how various in color they can be. The Mushroom Expert's key for identifying this mushroom is very useful. The key features: thin and leathery, strikingly different concentric zones (often in many different colors), a somewhat hairy surface, and a white pore surface with pores just barely visible. With a hand lens you'll see that the pores are about 4-5 per millimeter.
The various Stereum species (see False Turkey Tail) lack a pore surface.
Trametes pubescens and Trametes ochracea are less distinctly zoned.
Trametes hirsuta is hairier and thicker and often concentrically sulcate.
See also my post on Trametes villosa.
Turkey Tails are frequently used as medicine. They have been shown to be immuno-modulatory stimulants and to have anti-viral properties. Paul Stamets sings their praises in the documentary Fantastic Fungi.
The next two photos are of some Turkey Tails I found on July 30:
