We've been using quite a bit of chalk lately. It's such a fun way for the kids to practice writing and since it washes off, I basically let them chalk on everything. As you can see in this picture, there's chalk on our grill, our fence, our porch, our garbage can, and even the kids' bikes. My husband mentioned that it was starting to look like a graffiti artist lived at our house. I laughed, but then looked out and realized he was right. That afternoon, we headed out with two pans full of soapy water and two sponges with the task of cleaning up our back porch just a little.
My boy mostly splashed around in the bubbles. My girl, however, found this task very rewarding! She meticulously scrubbed the fence. With each fence post she would get really excited and shout, "Look how clean it is!" I think she found a lot of pleasure in this task (which is great! I've always wanted my kids to love cleaning!).
Shortly after she made it all the way around the fence, my son found a piece of chalk and started the artwork all over again. He would dip the chalk in the water and then draw, making the lines extra dark. That didn't deter my daughter for a second. She just followed right behind him, cleaning the trail he left behind.
Oh, and just for the record, the next day it rained and all the chalk that was left got washed away.