I read an article today by Mary Roach in Reader's Digest titled "Best Cheap Fun!" here are some of her thoughts:
Visit a photo booth. While you wait for your photos to develop, reach up and feel the top of the booth, people often toss their embarassing outtakes up there.
Bubble Wrap... Your cat. Blow into its face. Stick your finger in his mouth when he yawns, put a leash on him and try to take him for a walk.
Put an Elizabethan collar on yourself and then go driving around for awhile.
Attempt sneaking a bottle of water onto a plane.
Ride one of the 25-cent "horsey" rides outside walmart.
Root for the opposing team at a home game.
Lie down in a cow pasture. if the herd is farr off, start yelling to get their attention, and then drop immediately to the ground and lie flat. the entire herd will come galloping over and form a circle around you and stare down at you with intense bovine curiosity.