A Chemical Engineer that is an advanced DIY automechanic. He really pushes the concept of not being a parts changer.
I utilize Paul Falstad's Circuit Simulator to play around with circuit designs to understand how they work.
Auto Diagnostics and Publishing web site. They publish good YouTube training videos, teach you how to build your own test equipment, and sell unique automotive diagnostic tools.
Even if you don't own a fluke, the sections describing tests and how to interprete results are very informative.
A general list of troubleshooting procedures to help the DIY mechanic get going on an issue
One of the many great welders on YouTube. He taught me that MIG welding is something you feel and listen to.
Under the [Technical Articles] section, numerous PDF files can be downloaded with great automotive mechanic content.
An off-the-cuff Video Blog about Electronics Engineering, for engineers, hobbyists, enthusiasts, hackers and Makers
A Professional Mechanic that shares his experience, his daily jobs, and tips and tricks.
Able to view people's complaints for Year/Make/Model. You can also access Recalls and TSBs.