So after posting a few tiltshift fakes to my Flickr account, the most frequent response has been “Yeah, they look cool, but what the hell is ‘tilt-shift’ photography??”. Well let me quote myself from an email I sent to my mother as a response to just that question:
Tilt/shift lenses let you change the focal plane of your camera by shifting your lens up/down/left/right or by tilting it in any direction.  In this manner you can do lots of interesting stuff to change the field of view and where the "focal point" is on an image. They're used a lot in things like fashion and landscape photography to do things like selectively bring into focus a particular part of a photo. Check out the example fashion photo at the bottom of . For landscape and in particular photos taken at a high angle of city scenes, they have the cool side-effect of allowing you to create pictures that look like macro photos of highly detailed models, since you can shrink the field of view to a narrow plane of the photo a lot like a macro lens does. But I just fake it using a gradient mask and a lens blur in photoshop.  http://www.dennisonbertram.com/hackmaster/2005/02/tilt-shift-pc-lens.htm  http://www.photo.net/equipment/canon/tilt-shift
The whole tilt-shift miniature meme probably started with a post to Boing Boing with some awesome shots from a photographer who used a real tilt-shift lens to constrain his depth-of-field to make photos look like ultra-detailed models. And then, as memes go, it took on a life of its own and spawned more Boing Boing posts, Flickr groups, Photoshop “hacks”, and so-on.
Ah, the joys of the intarweb…