Most economical transportation in Paris

It is possible to get a weekly Navigo pass but this only covers a calendar week from Monday to Sunday. For the days before or after the best choice is usually to get "carnets" of ten single-journey tickets, each of which will allow free transfers between different metro/RER lines or different bus routes (no free transfer if switching between rail and road transport). Day passes in Paris are not good value unless you're making six or more trips in one day, and the tourist-aimed Paris Visite passes aren't worth it.

Here's more information about the Pass Navigo Decouverte, which (as said above) is only valid Monday through Sunday: http://parisbytrain.com/paris-train-metro-week-pass-navigo-decouverte/

Ditto Phillip! If you get a month pass for zones 1-2 you can travel in all 5 zones on the weekends for free. We scanned our passport photos from home and resized them to fit the navigo cards. Printed, cut them out, and put them in a sandwich bag. It saved me 5E per person on photos. :)

I also used the Passe Navigo Decouverte last time I was in Paris and it took me everywhere. I used the Metro several times per day so a carnet would have been used up quickly. This time I'll be there for five days and it still makes sense for me so I'll be taking it back with me to recharge. Unlike London's Oyster card, it gives you unlimited travel. I printed my own picture which they accept, but be sure to have one as it is required. There is a lot to do in Paris for 14 days. Having a flash pass to their metro and bus system takes the hassle out of getting from here to there.

I worked out that at 4 days, I was going to break even or come out ahead on a weekly Navigo. That also meant I could just hop on a bus for a stop or two when I was too hot in the sun or my feet were complaining too much. There's a one-time €5 fee for each card. Be sure to take little photos with you, so much easier (and cheaper) than getting them on the spot. Once you are in Paris you can pick them up at most metros. You have to assemble them, then go back to get the weekly card loaded. It's also faster because at the busy metro stations there are stiles just for the passes, much quicker than the individual ticket stiles.