Other options for carsharing in Paris are Caisse Commune, which has prices ranging €12 to €25 for the monthly fee, then €2-3 per hour and €0.21-0.44 per km. Then there's also Okigo, charging €9.90 a month, €4 per hour and €0.35 per km. Finally you can also rent a car for less than a day at Hertz, which offers 4, 8 or 12-hour rentals for €35. There's a demo video after the jump.
The video meant to be presented here is no longer available. Sorry for the inconvenience.
[Source: Le Monde (h/t to Dominique for the tip)]