Here is an science and art lesson. One of our science units is about states of matter and we mostly talk about solids, liquids, and gases. In order to help students experience air I plopped down some paints and let them go to town and blow as hard as they could. I gave them very little instruction beyond blow the paint and keep it on the paper. Some of them really got into mixing the colors and it brought up such wonderful discussions.
A few tips.
Make sure your paint is watery so it will move around, but not too watery because then it will run off the page on onto your tables and floor...not that I would know anything about that. :)
Also try to get those little straws like they have a lunch for their milk. The thinner the straw the harder it is to blow. This is good because you want them to have to work at it.
Another handy tip I have is for how to dry painted paper. Since I have a limited amount of space I take a Styrofoam tray (I just used ones from the lunch room that the kids were done with) and cut paper to fit inside.
Depending on what you are doing you can have the kids paint with the paper already in the tray or place it in when they are done.
Then just stack them up criss cross.