Tinkercad-online 3D design and 3D printing
Thingiverse-sharing 3D printable things
MIT App Inventor-programming tool for building Android apps
AdaFruit-tools, equipment and electronics online store
Make:-DIY projects and ideas
Autodesk Circuits-design, share and produce electronic circuits
Code.org-learn to code
Gamestar Mechanic-the principles of game design and systems thinking
How Stuff Works-articles and videos teaching how stuff works
Big Huge Labs- Do fun stuff with your photos
Scratch-free visual programming language