"What's the future ever done for me?"
I'm trying to do the same thing with then-and-now photos of remaining Nazi sites here in Germany and would love to learn how to use photoshop to create the kind of image you have as an heading to your blog and those of Sergey Larenkov, a photographer who blends photos from WWII with current ones: http://sergey-larenkov.livejournal.com/
It's quite simple really.You need 2 photos, the original and the current taken from the same vantage point.Open both in Photoshop as separate layers and adjust the size so that they both line up.Then use the eraser tool @ 20% or so and start to erode the current (top) photo revealing the past underneath.If the photos are a good match it shouldn't take long at all.
I had a look at your site. Very interesting.I might post a piece on the process soon.
Cheers GBC- The obstacle was simply figuring out how to open up layers, but I had a student show me and by 20 minutes I was off and running. I've made dozens already of varying degrees of quality. You can check them out at http://www.facebook.com/media/set/?set=a.10150209293359962.321308.505494961although they're mostly Third-Reich related at the moment.