I recently stumbled across a site that could keep me busy for hours. Waymarking calls itself "a scavenger hunt for unique and interesting locations in the world." While some of the posted locations are probably not interesting to genealogists (I doubt McDonalds was around when my ancestors were there), others can help you flesh out the historical details of the area.
You can search or browse the site. If you browse, it's by category rather than location so I prefer the search. The search box is right on the home page. Just put in a keyword (if desired; I left it blank) and a location. The default distance appears to be 100 kms, but you can adjust this by using the additional search options.
For the purposes of trying it out, I put in Sparks, GA and narrowed it down to a distance of 10 km (a little over 6 miles), which is where my great grandmother lived as a child. It returned 23 records. These included pictures of the veterans memorial, the courthouse, a local cemetery, a state park, several historical markers and a few miscellaneous items (rest area, McDonald's).
The amount of additional information provided varies. Many people have transcribed inscriptions on the markers, added information on the background or the exact location. Some have additional photographs when you view the full record.
I tried out several locations based on my ancestor's movements and never failed to find something in the area, although some locations required increasing the distance. Since waymarks are user-submitted, it depends on how many people from that area have uploaded items. As I said before, some of it isn't extremely useful for family historians, but I'm definitely interested in the possibilities for further research Waymarking can bring to the table.