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!
Laminate a set of flash cards, put a binder ring around them, and toss them in your purse with a dry erase marker to entertain little ones. I don't know about the dry erase part but LOVE the binder ring!