Google last month introduced a time machine feature to Street View on Google Maps for the desktop, letting you choose a past date for locations where Google's Street View van has passed by more than once.
For a location where there is only a single set of Street View imagery, you'll see the month and year the image was taken beneath the address. For my small city in New Hampshire, for example, I now know that the Street View van came through in August 2011.
If I head south to Boston, however, I'll encounter the new Street View time machine. I plugged in Fenway Park, and next to the banner with the date of when the current image was captured, there is a small clock icon with "New" written in red text. Clicking on this banner opens a small window with a slider of dates that stretch back to 2007. As I select different dates, I can preview the image for each date in this small window, and by clicking on the preview window, I can open a past date in Street View. I can then walk the streets in Street View in the past.
While I was able to see Fenway in September 2007 -- just before the Red Sox's second World Series championship -- I was unable to go back any further to the dark days of The Curse and chants of 1918. If you'd like to see how your house or favorite landmarks have changed over the past seven years or so, however, Google Maps provides a fun way to take a trip down memory lane.
(Via Here's the Thing)