This organism has a number of common names: sulfur shelf, sulfur polypore, chicken of the woods and, by a handful of people, tree brain (though this common name is more often associated with Peniophora rufa).
The name Laetiporus sulphureus was previously applied to a wide-ranging North American species that grew on a variety of substrates. Upon further examination, however, fungal taxonomists have split up the old Laetiporus sulphureus into a number of separate species. The current Laetiporus sulphureus, pictured here, is native to eastern North America and grows on (in) hardwoods. To give an example of one species that has been split off, Laetiporus conifericola is native to western North America and grows on conifers. Tom Volk tells the story in his page on Laetiporus cincinnatus. He also discusses the common name “chicken of the woods”, which apparently is how it tastes when cooked properly, though I haven’t tried it.
Photography resource link: Macro Art in Nature is a macro photography weblog by Michael Brown of South Carolina. His abstracts are worth your time to investigate. Michael posted a couple comments to BPotD yesterday, which was a bit of a coincidence–without any correspondence between us, I had planned to suggest his site as today’s resource link.