Check this site from Joy Sikorski (aka Joy Radish).
Lots of clever drawing ideas and lessons for
"For Grown-Ups who are Fun, and for Smart Kids
(and All kids are smart, of course!)"
The lessons reminds me of Ed Emberly's 'how to' lessons and are great for kids learning shapes and their relationship to each other to create bigger images.  
And with the Headline
"ALWAYS HAVE FUN AT WORK, that's what work is for"
Joy also gives us great projects to amuse yourself in your cubicle.