Go on a Scavenger Hunt
Limit the territory to the backyard or the inside the house and kids will suddenly notice objects that they usually overlook. Set a time limit (a half hour for 20 clues should do it), and supply each child with a bag to hold his booty and a list of clues. Spark their imagination with things that are open for interpretation, like “something that smells really bad” or “an object that starts with the letter K.” (This also keeps the kids from clobbering one another while racing to the one blue spatula.) When time is up, tally who found the most items. Aside from bragging rights, the winner gets a fun prize, such as a gift certificate to the movies or the ice cream shop.