Easy and fun.Velcro + popsicle sticks make for great quiet time or restaurant activity. Put velcro dots on the ends of popsicle sticks. Kids can make letters or shapes over and over again. I found velcro dots at my local dollar store.
Make a wind chime out of old keys and acrylic paint. - This site has lots of cheap outdoor/backyard ideas. I can't use most because I live in an apartment - but I love the old key to windchime and spray painted folding chairs.