Tux Paint 

Tux Paint is a free, award-winning drawing program for children ages 3 to 12 (for example, preschool and K-6). It combines an easy-to-use interface, fun sound effects, and an encouraging cartoon mascot who guides children as they use the program.

Kids are presented with a blank canvas and a variety of drawing tools to help them be creative.

Tux Paint for Mac OS X comes as two disk image (.dmg) files. One contains main program (Tux Paint) and a configuration program (Tux Paint Config.) for parents and teachers. Copy them to your hard drive's Applications folder. The other contains an application that installs the optional 'stamps' collection.