As a side-project I'm trying to create an app that scans license plates from passing cars from my living-room window.
I have hooked up a high resolution camera to my system to capture (moving) images into my c# app. Now all I need is a way to interpret these images into something readable.
I´m thinking about some sort of OCR-solution that is fast/accurate enough for moving images.
Hope you can give me some direction!
You'll need to search on ANPR, although I'm unsure whether there are any free libraries available due to its high commercial use.
CARMEN is a commercial product that is apparently free for private use. It's C++, but offers a C# API.
Note that, depending on where you live, collecting this kind of data may be illegal due to privacy laws. I suggest you spend some time researching that topic, or collect only statistical data (which is probably your goal anyway) while discarding all data about individual license plates.
If you plan to read number plates from UK you could try SimpleLPR, which provides a .NET interface. The license is shareware, 30 day trial. You can download it from http://www.warelogic.com
If you are looking to write your own, I would start with the AForge image processing libraries. Here is a discussion about doing license plate recognition in the context of AForge.
They also recommend JavaANPR, SimpleLPR, and ANPR if you are looking for out of the box solutions.
Check out the Emgu CV project which is a wrapper for the OpenCV library. One of the samples is license plate recognition application...