www.rt66pix.com has more than 1700 Mother Road images, including (at last count) 398 of the road surface alone. Everything is grouped by state and category. There's a Route 66 Sampler Trip...even a gallery of 66 images designed for kids.
Other material includes the National (Cumberland) Road, and Roadside Americana. Hundreds more show classic cars, neon and the like. If you want to waste some serious time--check out the "Fun!" section with more than a hundred loopy questions.