DNA extraction is a fun way to experience what DNA actually looks like. I have performed this lab several times in the 7th grade classroom, as well as with my eight year old daughter. The University of Utah does a nice job of providing links online, which answer commonly asked questions. They also provide a pdf copy of the webpage, which works as a handout for students as they follow the steps in teams.
I could also see this being used in high school or college Biology classes.