When the tree leaves stop producing chlorophyll for the year and the green stuff starts to break down and disappear, the other colors of the leaves, hidden all summer, are exposed and have their moment in the sun: yellow from xanthophyll, red from anthocyanins, orange from carotenes, and brown from tannins, the leaf's waste products. New York's Buffalo Museum of Science has a really good explanation of it all.
We were in Vermont with my brother and sister-in-law a week ago and this kind of sight was unavoidable. Besides a lovely walk in the woods on the Marsh-Billings-Rockefeller estate, we visited Ben and Jerry's factory in Waterbury and the Hope Cemetery in Barre. (Check out Neil's page for great photos of the cemetery markers.) There was a roadside waterfall, milkweed seed pods ready to be picked, and good barbecue to eat. A fine weekend all around. More photos on my Flickr page.