Google Earth/Historical Imagery

I have used Google Earth before and have been able to see some very interesting things.  I have never used the 3D option though, that was very cool to use around stadiums and in big cities.  The historical imagery was also new to me, it was a little blurry and hard to see some of the buildings and roads.  This would be very useful for students from 3rd grade on up to see how each city has changed over time, what New York looked like before 9/11.  It would be useful in small towns such as Scottsbluff for the students to go see how this town has grown over time and what areas have been developed over the years.