Sometimes (actually, most of the time) the best activities don't need any materials... except maybe a big hill or a little bit of magic from the sky,
Somersaults down a tall hill... again and again and again
Rolling sideways down the same hill and getting covered with newly cut grass
Watching an insanely intense rainstorm from inside the car... and then jumping out and doing a little dancing... and getting soaked (no pics of the dancing- we were having too much fun... or at least I was ;)).
What's your favorite simple summer activity that requires basically nothing- no glue, no basketballs, no dot markers- absolutely nothing... except you and your kiddos and nature?