As you may know, MapQuest recently discontinued aerial photos. But you can get hi-res aerial photos for about 40 US cities (sorry, NY, SF and LA not included) at http://seamless.usgs.gov/viewer.htm. The site is a bit hard to use, but there are step-by-step instructions at http://cryptome.org/sdds-guide.htm.
You can download a TIFF of any selected area. They’re big files, but they’re worth it - the detail is stunning, far better than MapQuest. I downloaded a view of the Museum of Science and Industry in Chicago. The picture was taken before the U-505 submarine was moved indoors, and you can see it clearly.
Interestingly, the cryptome site says that the areas around the White House and the Capitol are blurred out.
You MUST try the USGS site. On the TIFFs I downloaded for Chicago, a car takes up about 20 pixels in length. That actually seems to be more than their stated resolution of .3 meters, so I’m not sure what’s going on. But the TIFFs are great no matter what the exact resolution it.
The USGS has another way of getting to aerial photos - http://nationalmap.usgs.gov/index.html. The interface is similar to the previous site I mentioned, but it also can get images from Terraserver where hi-res images are not available. You can also display topo layers from Terraserver (and yes, I know of other places to get topo maps). You do have to fiddle with the layers a bit to get the images you want.
Completely off topic but… this thread just gave me flashbacks to a college course on Soil Identification and Interpretation (I was an archaeology major, lots of Earth Science courses) where we took a field trip to look at some blue clays… and got lost. And had to try to make it back home using topo maps.