Cronobook is a new-to-me website that features a searchable map of historical photographs. The premise of the site is simple and using it is easy. Just head to the site, search for a location, and click on the small images to see them in full size. A little bit of information including location and date is included with the images.
Cronobook is still a beta product so that breadth of the imagery is fairly limited. You'll have better luck finding historical images if you stick to large cities as compared to small towns. It should also be noted that just because the images are old that doesn't mean they're not copyrighted. Check the image licensing before downloading any images from Cronobook.
In a lot of ways Cronobook feels like a lightweight version Historypin. Depending on your perspective that could be a good thing or a bad thing. I like it because it's a little easier to use.Applications for Education
If you're a history teacher, Cronobook is one of those sites that is worth bookmarking and consulting when want to show students what a city looked like in the past. It could also be a good site for students to explore on their own to inspire some curiousity for learning more about the history of city or neighborhood within a city.