Hour of Code

Lots of options on Hour of Code.com

I recommend: 

First Grade- Kodable

Second Grade- The Foos

Third Grade- Lightbot

Fourth Grade- Code.org - Minecraft Voyage Aquatic

Fifth Grade- Scratch Cartoon Network Adventure Game

Sixth Grade- Google Grasshopper

Other resources

Compute It

Snoopy's Snowball Fight

Harry Potter (code.org)

The Grinch

Google CSFirst Code Your Hero

Google Santa Tracker Codelab &

 Santa Tracker Code Boogie (Only available in December, best for primary grades.)

Lego- Bits and Bricks

Pixel Hack

Made With Code

Scratch

Blockly

Code Combat

Code Monkey

Code Monster

REPL

CodeAcademy

Khan Academy