It's a photography effect called Tiltshift. I've got some fantastic photos from our honeymoon of parts of San Francisco that look like they're in miniature. To be ironic we also did it to a life-sized version of one of those Games Workshop tanks too; it looked like a better miniature than the actual miniatures
There's a website that lets you do them very quickly too, called Tiltshift Maker:
http://tiltshiftmaker.com/
The best photos are the ones where there are lots of things in shot; close ups rarely come out very well. Also, daylight and bold colours look best after the effect it applied.
For example (and sorry for filling the thread with these, this is it, promise):
None of those are actually miniatures