Inkscape is an open-source drawing tool, comparable to Illustrator, Freehand and Corel Draw. You can create games for your students, access a huge library of innovative cliparts, or you can have your students create flags and maps. Here’s a gallery with some examples. And here’s where you can download the program. I would certainly recommend that you take a look at a tutorial first.
The website is clean and gives helpful tips for beginners. I think Inkscape is useful if you want to create something sophisticated that can’t be done in an easier way, e.g., with the drawing functions in WORD, because the learning curve seems to be rather steep. But then again, it’s amazing what you can do with Inscape.