I've discussed how to use tilt-shift to fix a blurry photo. It can also be used to create "miniature" scenes. Here are some great examples. One of my favorite tilt-shift photographers is Keith Loutit. He actually makes time-lapse films from his shots.
Here's a great tutorial for tilt-shift. I do want to add something to it, though. Once you've added the lens blur, slightly blur the left and right sides of the focus area with the Blur Tool. I find this to be a more convincing miniature.
For those that don't have access to a program like Photoshop, use the online Tilt Shift Maker. Try it out!
The two top photos don't quite look miniature, do they? This technique works best on shots taken from above.