I learned about this site from @Ktenkely on her website iLearntechnology. It's an interacitve site that allows you to create Jackson Pollock style paintings without any of the mess. This is great fun on the Smartboard. By clicking the mouse you change to a random color and splashes of paint appear as you move the mouse across the screen. JacksonPollock.org is a wonderful site that art teachers can use that will save you a big cleanup in the future.
-Give it a try!