click to enlarge, or see it on Flickr
I faked that image in Photoshop; it really is just a picture of a street in New York from a high vantage point. As you can see, I didn't do a perfect job on it—if you look up faked tilt-shift pictures, you'll find ones that are done much more convincingly. This group on Flickr, for example, has a number of excellent shots.
There are a number of ways to fake tilt-shift photography, none of which I want to explain. There are tutorials out there for Photoshop, but the easiest way is to just use Tilt-Shift Maker. I've never tried it personally, but I've seen an image that came out of it, and it was quite well-done.
Feel free to leave me feedback, especially constructive criticism (that goes for all my posts; it's why I started this blog). And if you have a great tilt-shift picture to show the world, post a link to it in the comments!