Hi
I am currently working on a very basic home security system project with motion sensors, door sensors and vibration sensors. I have got most of it up and running but the problem i have now is taking snapshots using a standard USB webcam and storing the photo on my computer when one of the sensors are triggered. How do i use the arduino to trigger the webcam to take a photo?Any suggestions would be greatly appreciated 
This isn't a well thought out answer by any means, but just "off the cuff" I thought if you have a cheap-o digital camera you could disassemble it, and wire a transistor in to the shutter-button wiring. Then use a trip wire, or motion sensor to snap off pictures when there is something activating your trigger motion/trip trigger.
Not sure if this helps any, sorry for massive run-on sentences! I'm so sleepy... Must nap... lol. Good luck on your project it sounds awesome!