Navigo Card

David Lebovitz recommends the weekly Navigo Découverte card that runs from Monday morning to Sunday evening. You need to pay 5 euros for the card and need a small photo of yourself but it is only 16.80 euros compared to 29.90 for a 5-day Paris Visite card. Lebovitz has a posting on Paris Transit Options as well. Here's the official Navigo website and further information from Paris by Train. It says don't let the clerks at the station intimidate you by saying it's not available to tourists.