I’ve had brakes stolen and neighbors have had their bikes stolen out of garages. I’m lucky that I don’t need to park my bike downtown or outside. I carry a spare shifter cable and I’d consider spare brake pads if I had to park outside as well.
I’d also avoid commuting with an attractive bike–good looks create more of a target.

http://www.bikecommuters.com/2010/11/27/properly-lock-your-bike/

There’s also a guide out there describing how to lock your front wheel to your back wheel and frame with a U-lock.