Through August 24 The Paris Fun Fair (Fête Foraine) is open in the Tuileries (Louvre Gardens), daily 11am-11:45pm (until 12:45am on Friday and Saturday). Free entrance, but you’ll need to buy tickets for each ride on the usual carnival attractions, or have cash for cotton candy and the games where you can win prizes. The Ferris Wheel has excellent views over Paris!
Through August 24 The annual Open-Air Cinema Festival takes place Wed-Sun nights at the Parc de la Villette's Triangle Prairie (M° Porte de Pantin), starting at sunset (around 10pm), free entry. This year's theme is Adolescence, including films such as Moonrise Kingdom, Scream 4, and American Graffiti.
Through August 31 Between the Lines and the Trenches, a very intimate collection of personal letters, notebooks and photos from the trenches, many never published before. At the Museum of Letters and Manuscripts (222 Boulevard Saint-Germain), through August 31st, entry €7.