Bottle Bank via Martha Stewart: transform a used plastic bottle into a cute piggy bank. Could use same idea to made little containers for kids to store their collections too (use bottle with wider opening and don't make slot)
Funny, easy crafts that use discarded household items are some of my favorite things. Make your own Faux Animal Head Taxidermy using detergent bottles, orange juice or milk jugs. Kids get the biggest kick out of these!