Many hackers would probably find car maintenance/repair a very satisfying hobby. I find working on cars/motorcycles to be very similar to writing applications, only with the added bonus of being tangible and real.

You don't necessarily have to do all of your own work (tools and time dependent), but once you learn how to do a lot of it, and have gotten your hands greasy enough, you can talk to mechanics intelligently and straight, and can tell BS when you hear it.