Marble Races with a cheap pool noodle (occupies the kids for hours.) Did this, but instead of cutting the pool noodle, the marble is small enough to fit inside the full noodle to roll down. Then can use the noodle for other things too!
Fun Kid Activity: Lines of Colored Tape, straws and pompoms. Try straws and cotton balls. Adding the lines ups the challenge. Using pompoms allows you to adjust the size from tiny to pretty big. The pompoms are also nicer looking.
Yo-yo painting--this looks so fun Fill a cut-off stocking with dry beans (I'll probably use rice, because that's what we have). Dip it in paint, then pretend it's a yo-yo and bounce it on a piece of paper. So fun!