What to do with yourself on a rainy day ?
Well, you could visit the Paris Salon de la Photo which is now in the Porte de Versailles Parc des Expositions. The annual mass for photographers will let you try all the new products whether they are cameras, lenses, papers, monitors, programs... In principle you have to bay for the entrance but it is so easy to find a free coupon on internet.
Last day is Monday next, so hurry !
And take your own camera with you and try shooting a portrait of one nice lady of the staff. There are even models parading on some stands.