I've been spending the last couple hours flicking through this goregeous set on Flickr. It's been uploaded by the Library of Congress and is comprised of about 2000 images from the 1940's- in color. They're beautiful and entrancing- they range in subject from urban sprawl to wild west; from farmer to rosie-the-riveter types. Most of them are Kodachrome proccess, giving the colors that special detailed saturation that only that proccess could acheive. I can't get enough of it. Best: no copyright. Worst: idiots putting 10 million comment boxes on everything.
Just as an interesting side note: there is only one place in the US still proccessing kodachrome.