Project Alica shows a great way to make star shaped sidewalk chalk. She uses red white and blue for the fourth of July but you can use any shapes and colors to make these all summer long. The plaster of paris is the hard to find ingredient but as she mentions your local hardware store should have it.
Good for ages 9 and up.
Get the instructions here:
http://www.projectalicia.com/2010/06/not-so-wordless-wednesday-diy-4th-of.html
