Embedded Computing/Microcontrollers

Adafruit
http://learn.adafruit.com/

Arduino
https://www.arduino.cc/en/Guide/HomePage

Instructables
http://www.instructables.com/

ITP Physical Computing
http://itp.nyu.edu/physcomp/

Let's Start Coding.com
http://www.letsstartcoding.com/all-base-kit-projects

Makey-Makey Keyboard Interface 
http://makeymakey.com/guides/

Maker Education-Tools and Materials
http://makered.org/resources/tools-materials/

Machine Science Tutorials
http://guides.machinescience.org/course/view.php?id=29

Project Ignite
https://projectignite.autodesk.com/

Raspberry Pi-Physical Computing with Scratch
https://www.raspberrypi.org/learning/physical-computing-with-scratch/

Scratch-X Extensions- Arduino 101, Leap Motion, and More
http://scratchx.org/#extensions

SpoLearning Labs( Liz Arum)-3D Printing Resources
http://spolearninglab.com/curriculum/lessonPlans/index.html

Sparkfun
https://learn.sparkfun.com/resources

Technology Will Save Us
https://www.techwillsaveus.com/resources/