While I have a formal Mechanical Engineering degree, my university focused largely on theory rather than practicality. As such, most of what I have learned about science and technology has been from the internet.
Here are the pages that taught me the skills I have today.
Imajeenyus is run by a gentleman who really is brilliant in the wide breadth of projects that he dabbles with and walks you through the science of what he does.
Dave Jones runs a fantastic video series called the EEV Blog. If you want to learn about Electrical Engineering, this guy can keep you entertained for days. http://www.eevblog.com/