The Fete foraine du Jardin des Tuileries is a small amusement park that is set up every summer between the beginning of July to the last Sunday in August in the Tuileries Gardens (right next to the Louvre).
About sixty attractions are set up, from the classic fun fair rides, to authentic wooden horses, Big Wheel, dodgem cars, duck fishing, etc. It is a good place to bring the kids.
The big wheel also gives you a unique and great view on Paris. It just closed last Sunday, but the big wheel gets re-installed from mid-November to mid-January on Place de la Concorde. So don't miss it if you come during that time.