SCAN is an After Effects preset that let's you create a scan effect, and it has quite a number of controls. Before downloading, check it:
1. It's registered on Creative Commons! Loser :-P CC BY NC SA
2. Try push it and find some errors!!
Here it is at work in a quick demo:
In this ZIP you'll find:
1. The After Effects preset
2. A demo video
3. The AEP of the demo video
4. A Readme (that you should read to understand how to use it)
I've done the best I can to get rid of bugs, and trust me it shouldn't crash AE, but to be safe work with only one instance per layer (it won't work otherwise anyway but just to be safe).
Get it here: Scan Beta for After Effects (works with any version)
To get it working, just copy the file to Documents > Adobe > Adobe After Effects > User Presets
When you run AE it'll be in the Effects & Presets panel.
Enjoy!! Let me know what you'll pull off with this and any error you get either here as a comment or on my twitter @davdalx (link above).
EDIT: If you're having issues with render speeds, go to the Back/Foward edge and set down the Feather and/or disable the Glow.
Cheers!