art

Tux Paint is a free, award-winning drawing program for children ages 3 to 12, it is used in schools around the world as a computer literacy drawing activity. It combines an easy-to-use interface, fun sound effects, and an encouraging cartoon mascot who guides children as they use the program. Available for Windows, OSX, Linux, Android and iPad.

You can download the Windows and OSX versions from here as well as the source code; on Linux, Android or iPad search for Tux Paint in your software installation tool. Free/Open Source software, by New Breed Software.