This seemed like the best place to post this :)

Big brother has it, so why not you too.
Automatic (or automated) license/number-plate recognition (ALPR / ANPR).

1. A suitable IP camera
2. Spare computer
3. Internet connection
4. A bit of reading

Bam, search able, alert able database of passing cars.

The longer version.

I have cameras up around my house.
They were not great but enough to see people and stuff.
One day my neighbour got their car stolen at 1130pm.
The thieves parked up outside in view of one of the cameras.
The camera was geared to protecting my property so something on the periphery was not going to look great.
Basically a black blob.
Was disappoint that I could not help this neighbour.
I current work as a security tech so this situation was akin to a doctor that smokes or mechanic that drives a rust bucket.
This would not do.

While they were likely using a stolen car on the prowl it still would have been helpful to get a licence plate.
Something for the police to work with.

A new camera was setup to watch the road capturing number plates.
Had to work well day and night.
This required some tuning to get right.

Then I wondered how far ALPR had come and went looking.
Quite a long way it seemed.

Settled on this after looking at various options.
http://www.openalpr.com/
For the home enthusiast it is free.
Got it going pretty good now.
Missing about 1 in 30 reads for some reason.
Still troubleshooting.

Cost wise you are not looking at a lot,
A dedicated camera from china, $150
Computer, an old i3 desktop, $100

The catch is in the time to mount and tune the system.