A polypore found on dead and live trees.  I found this one growing on a live Red Oak in a park next to where I live in Shrewsbury:

It is soft, as compared to the Chicken of the Woods, and very attractive after cooking and slicing.  It has the appearance of sliced beef with marbling.  I do not care for it because it tastes like it was flavored with the juice of a lemon.  My taste buds tell me that a mushroom has no business being sour :o)