I really like the Tilt-Shift Blur tool in Photoshop, but there is no built-in equivalent in After Effects. So I made my own quickie version of it to use for a job I was animating. During the course of that project I added a bunch of functionality to the tool, and found it pretty darn useful.
I saved the After Effects project and if you're interested, check it out! Maybe it will save you some time or help you out in a pinch.
This is not a plugin or script, but an AEP that attempts to imitate the built-in Photoshop Tilt-Shift Blur tool.
For more info, please read this breakdown of the project on my website.
Here's more information about using the controls.