I read a review of TuxPaint by Marilyn Western in the Spring/Summer 2008 issue of the MACUL journal that landed on my desk just yesterday and I had to share it with my dedicated legion of readers. As Marilyn mentions in her review, TuxPaint is an open source alternative to KidPix, which means it is free and available for both Mac and Windows. I realize KidPix is available on both platforms as well but of course it isn't free. I encourage you to look over Marilyn's review for some great ideas on how you may use TuxPaint but really, if you have used KidPix you can do essentially everything you have been able to do with that software. If you aren't familiar with KidPix or applications like it, then check out the screenshots I have included to see some of the ways you can use this graphic arts/drawing program.
Students can create their own drawings, design habitats for an assigned animal, visually represent math problems, work with a teacher created template, insert personal pictures in their creations and much more. It is definitely worth a look and the price (free) is certainly right.