Instructables: huge website with all sorts of step-by-step instructions on how to make cool stuff. Post mastery level projects here.
Adafruit: the best website for electronics / coding based projects. It is also the website where I buy most of the electronics for DTech.
Inventables: Great source of information for CNC operation, particularly when using the X-carves. Website also features a huge list of materials to purchase. I use this website all the time.