Arduino http://www.arduino.cc/
Exploratorium: The Art of Tinkering http://www.artoftinkering.com/
Exploratorium: Tinkering Studio http://tinkering.exploratorium.edu/projects
IDEO Design Thinking for Educators http://www.designthinkingforeducators.com/
Google Made with Code https://www.madewithcode.com/
Instructables http://www.instructables.com/
The K12 Lab Wiki https://dschool.stanford.edu/groups/k12/
Lucid Chart https://www.lucidchart.com/
Maker Camp http://makercamp.com/
Make http://makezine.com/
Popplet http://popplet.com/
Sparktruck Resources http://sparktruck.org/resources