I'm working on getting my PPL, and I would like to read more about the specific causes of small private aircraft (single or twin prop, primarily) crashing, especially those that were caused by pilot error. Are there any good books or other resources on this matter? A decent amount of searching hasn't turned up much -- it seems like the data from private charter jets is often combined with that of the aircraft I'm interested in.
The AOPA's Air Safety Institute has quite a few resources that I like to review from time to time, including some great videos with commentary on exceptional cases.
I do exactly what you are doing, during training and still after, but I'd like to also say that you shouldn't narrow yourself to GA crashes, a lot of what happens commercially can be applied to GA, and usually with commercial accidents there is a lot more data and analysis available to work with. In that regard, I like to watch shows on Youtube like "Air Crash Investigation", or on TV like "Why Planes Crash" (some available on Youtube)
AOPA also has a lot of resources to view NTSB reports on individual crashes where you can search by certain criteria like aircraft type, states, type of flight, or even some specific keywords like "Vacuum Failure".
Just don't limit yourself to looking at things like "Pilot Error", pilot error is a broad category of crashes that is usually used to describe the pilot doing something wrong in the air, but a lot of crashes are "pilot error" in that the pilot could have broke the accident chain much earlier in the flight. Read as many as you can, regardless of the cause. For example an accident where the aircraft breaks up in flight may not be attributed to pilot error, but its good to know what lead to the break up and what could have been prevented.
The National Transportation Safety Board investigates vehicle-related accidents in the United States and publishes "accident reports" which includes details of the accidents and the findings of the investigators. Go nuts.
Aviation Safety Network is another good place to look.