Actual Coordinates:
North DI° AB.LCN', West FGJ° HE.OMK'
The coordinates for each location are from the bottom tip of the marker, not from the center of the image. Some of these will be very easy, and some will be more difficult. The key to some of the locations is to recognize a famous landmark in the picture, while others may require more subtle deductions. You should be able to get within a few miles or so before you need to start scanning about to find the exact location. If you click on the picture, you can get a higher resolution image.
The images I used here were pulled from the web on March 8th, 2011. Note that the old links to the full-size images (which you'll definitely need to make out important details on some of them) don't work anymore, but you can find all those pics here.
Thanks to DJHobby for giving me the idea for this puzzle.
North **° **.***', West ***° *A.***'
North **° *B.***', West ***° **.***'
North **° *C.***', West ***° **.***'
North **° **.D**', East ***° **.***'
North **° *E.***', East ***° **.***'
North **° *F.***', East ***° **.***'
North **° **.***', East ***° *G.***'
North **° **.H**', East ***° **.***'
North **° **.***', West ***° *I.***'
South **° **.***', West ***° **.J**'
South **° *K.***', West ***° **.***'
North **° **.L**', West ***° **.***'
North **° **.***', West ***° **.M**'
North **° **.***', West ***° **.N**'
North **° **.O**', West ***° **.***'
Note on terrain for the final location: The last 10-20 yards or so to the cache is a fairly steep, but not rocky, climb. You'll may or may not need to use your hands to get up there. Some have claimed that the terrain rating should be harder. It definitely isn't a 5/5 as you don't need special equipment to get there, and I typically think of a 4.5/5 as the sort of cache you need to clamber up a short cliff or climb a tree or something. But maybe it should be a 4/5. I'm going to leave it as a 3.5/5 for now, so as not to screw up the rating/terrain grids of people who have already found the cache, but I've added this note so that no one is too surprised when they get to the final location.