Credit Mutuel building in rue des Francs Bourgeois, 3eme. It is literally a two minute walk from my house, yet I only managed to get around to it yesterday. Amazing how I don't have an hour or so to spare sometimes.
Le Mur, which is a licensed, curated space on rue Oberkamp in the 11eme. With work that changes second Saturday, it's worth checking that out too.