Good beginner book/website for physical computing?

Not really a direct answer but one non the less, If you want to start learning about physical computing I would first start looking at books about micro controllers(using and programming them )and then move on from there. Micro controllers would allow you to control leds,etc. I'd give you a book but since each micro controller is different, it will have a different book for each. Any will do, just pick one that will suit your budget and read/go from there.