This post is just for my own notes. I'm buying a new car (arrives in October) and I need to gather up notes on how to hack it.
To start with is the generic car hacking information. One good source I found is the Car Hacker's Handbook, which has a good explanation of the basics.
Another good start is the various papers produced by Charlie Miller and Chris Valasek, such as their early work and their latest Jeep hack.  
Specifically to my car, a Tesla, there is this site that documents all the undocumented bits about the car, such as listing the 56 CPUs found in the car.
Specifically, there is the work by Kevin Mahaffey and Marc Rogers covering their Tesla hacking. I hate them, because they've already done some of the obvious things I would've tried first, such as popping up an X Window on the display.
Anyway, this post is for my own benefit, so when I lose my notes, I can find them again by googling. Maybe other people in similar situation might find it a bit useful, too.