look at historical imagery in Google Earth by using the time slider. Now a similar feature is available in Google Maps. As announced on the Google LatLong blog, now when you're viewing an image in Street View you may see a little clock icon in the upper-left portion of the screen. When you see a clock icon while viewing a Street View image you can click the icon to roll-back the view to a previous image. Google began publishing collections of Street View imagery in 2007. The number of images available will vary from location to location.
Applications for Education
Going back in time with Street View imagery could be a good way for students to see how some places have changed over the last seven years. This could be particularly useful when looking at locations that have suffered some type of natural disaster like a flood or earthquake. For older imagery on Google Maps, take a look at History Pin.