One is the Green Festival in Washington, D.C. It's this Saturday and Sunday (Oct 6, 7) at the Washington, D.C. Convention Center. Check out http://www.greenfestivals.org/content/view/625/280/ for more info.
And here is a link to their Kids' Zone activities http://www.greenfestivals.org/content/view/780/278/.
Looks like a lot of fun!
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