TiltShift is an OS X application for computer-generated tilt-shift photography. The software allows you to create fake-miniature versions of regular photos, simulating the effect of expensive tilt-shift lenses.
You can define an arbitrary position for the virtual focal plane and setup its properties using an intuitive visual interface. Additional controls for saturation, contrast, brightness, sharpness, and vignette let you create amazing fake miniatures.
Note: The downloadable demo is at 1.4. The version available for purchase on the Mac App Store is version 1.4.3.