Tuxpaint is a popular free drawing program designed especially for kids. It features quirky sound effects and a simplified interface that is ideal for younger children. All the basics that you’d expect in a drawing package are available, including brushes of various sizes and styles, shape tools, and a collection of ‘magic’ effects that can be applied to a drawing.
The best feature is a great set of stamps that lets kids plonk down fully formed cut-outs (animals, coins, hats, spacemen, food, symbols etc) into their work of art. Here’s one that AJ prepared earlier:
I think that’s Air Force One cruising past a meat pie.
Tuxpaint is available for most operating systems including Windows and OSX, and it’s also well suited to being run on older computers. If you download it, be sure to also download any additional stamp packs that have been made for your operating system’s version.