Another pinner says: Mess Free Finger Painting! What an awesome idea! Paint in a ziploc bag taped over a piece of paper. Of course we'll have to REALLY finger paint sometimes, too, since getting messy is half the fun.
DIY Portable LEGO Kit with Free Printable Activity Cards. I like this for school, older kids can have activity cards to create planets/atoms/molecules/fractions, younger ones can practice fine motor skills.
this one sounds even easier to make: bubble snakes = easy quick craft. Cut the bottom off water bottle. Put old sock over bottom and duct tape. Add food coloring for fun. Dip end in dish soap mixed with a little water