Great Open Source Drawing Tool
Up until now we’ve been using a drawing program (KP) that’s been pretty buggy and has incredibly obnoxious sound effects, not to mention a heinously annoying little intro song. (otherwise, I like it. no, really.)
Tux Paint is free, simple and incredibly fun. I love the interface, the Lynux penguin and the funny sound effects. It’s got the same types of bells and whistles, just more subdued and tasteful.
There are Windows, Mac and Lynux versions. Being open source, there’s great flexibility to tailor the program as much as you want, and the documentation is in plain English. But the basic install is excellent, so you can also just install and go without any changes.
It passed the 5 year old test 
and will soon be running on all my school machines.