One really quick test at the Herald Sun: Right Brain v Left Brain.

You'll look at a picture of a spinning dancer -- which way does she spin?

And here is another from the Art Institute of Vancouver: Right Brain vs Left Brain Creativity Test. There are 54 simple questions that are scored and evaluated. It takes 5 to 10 minutes, but reading the results were fun for me (and many described my "methods" of thinking and processing quite well).