What a fun way to assess understanding in the middle school math classroom! At Math in the Middle, you can learn about an assignment that asks students to create a comic strip teaching someone how to graph a linear equation in Standard Form. I love the uniqueness of it and I also love how it allows creative and linguistic students to shine (not always the case in math class). This idea could be used for many different math concepts, of course, and would be easy to adapt for other subject areas.
Keep in mind that an easy way to create different levels of challenge in this assignment is to ask different students to illustrate the teaching of different concepts.