Some neat collections compare historical scenes to present-day scenes:
1) Calgary: “Comparing 15 historic Calgary postcards with the same scene today” – via JH / CO on Facebook. (Thanks for sharing!)
2) Montreal: Comparing photos of Montreal from 1860-1935 with 1999 photos – via the McCord Museum.
3) “Why They Fight: Civil War Re-enactors and the Battle over Historic Sites” shows re-enactors at historic battle sites that have been changed by modern development.
4) The “Atlas of the Historical Geography of the United States” showcases change over time through historical maps – via Joseph Kerski of ESRI.