Grandparents.com has launched a major national campaign to get kids off the couch and outside to play this summer for a collective one million hours -- and they need help spreading the word. I'd love to pitch it to help them put an end to childhood stress and obesity. Grandparents.com has a free activity guide for all who get involved.
For more ideas for summer activities, check out this post from Marcia at Frugalhomekeeping. She's come up with great thoughts like, tie-dye.