Google Earth can be a great resource for genealogy, especially in conjunction with historical maps. I enjoy using the program to compare views of a place in the past to modern-day.
I found online a 1948 photo of Fields Corner, a section of the Boston, Massachusetts suburb of Dorchester where my father grew up. Then I used Google Earth to take, as closely as possible, a shot of the same place at the same angle to compare (fyi, I actually took this "new" picture a couple of years ago).
Amazing not how much has changed, but how little!