Paris metro passes

Yes, there is a one month pass. The catch is that it's for a calendar month, not just any thirty day period. You buy a Navigo Decouverte card (€5), then load it with a one month pass (€70). More details here, from Paris By Train: http://parisbytrain.com/paris-train-metro-week-pass-navigo-decouverte/. And details from the official RATP site, in French: http://www.ratp.fr/fr/ratp/c_21137/forfaits-navigo-mois-et-semaine/

It's not possible to buy it in advance. Just bring a small photo with you (you can print one on your computer). You can get it at CDG (even if you only want a 2 zone one), or at Metro and RER stations with staffed ticket booths (which other posts here indicate are getting more scarce).

Research whether you are better off just buying carnets, even though you're staying a month. Less hassle to buy.

If you aren't staying a calendar month, there are also weekly Navigo Decouverte, which cover a calendar week from Monday to Sunday. These are also cheaper than using carnets.

The reason you aren't finding these online on the English website is because RATP doesn't really want to sell these cheap passes to tourists, and would rather push the overpriced Paris Visite passes.

The Paris Visite is a total tourist rip off; there are almost no circumstances in which it would make sense. I would get a Navigo Decouverte for each person (there are no kid versions) and charge it weekly if your month is not a calendar month or monthly if it is close to a calendar month. If you are there more or less a calendar month then a pass charged for zones 1-2 would also be usable on weekends anywhere in the 5 zones so you could save your day trips out of town for the weekend. The weekly charge of the pass does not give you this 'dezonage' feature. You could patch the ends of the month with a carnet of ordinary tickets for 14.10. But if your month overlaps two months substantially e.g. June 15 to July 15 then the monthly ND won't work for you and just charge it weekly.

If you are using the ND to come in from the airport you can add a one time ticket for that trip at a savings -- a parcours. So you could have a zone 1-2 pass but still be able to use it from CDG to Paris with this added ticket. The ND runs from Monday to Sunday of each week (or as noted, a calendar month) so whether you would be able to use it for the airport trip depends on when you arrive. If you arrive say Friday then your ND would not be usable till the following Monday and you would have to buy an RER ticket for 10 Euro or take a cab for about 50.

Bring a postage stamp size head shot of each person for the NDs; they will sell you the kit and charge it and you will assemble the pass with your head shot. Any headshot of about 25/30 mm will do - you can print off at home on your computer after sizing and cropping.

Here is information on the Navigo Decouverte:

http://parisbytrain.com/paris-train-metro-week-pass-navigo-decouverte/

The picture should be about 1 1/8 inch high and 1 inch wide. I simply cropped one out of a family group pic and printed it on regular printer paper. Honestly, no one cares and no one looks at it. It is just so the pass is not transferable. You buy the "kit" for 5 euros and assemble it, which takes about 2 minutes. There's a sticky spot on the card where you put the picture, then slide it into the plastic case. Next you load it up for 1 zone or 5 zone (if you will be going outside of Paris). It is valid Monday through Sunday, then you reload it for the next week. You can't beat it for convenience. You won't need to keep track of tickets, which have limitations. For example, with the pass you can go anywhere in any direction at any time. With tickets you can transfer bus to bus, metro to metro, but not bus to metro or metro to bus, and the time frame is 90 minutes from when the ticket was first validated. In addition, you have to be going in the same general direction and cannot get off one bus, stop to see something, then get on the same bus line -- has to be a different bus line. With the pass - you just swipe it and it doesn't matter where you've been or where you are going. Added plus: it's valid for 10 years, so you take it with you the next time you go to Paris!

I LOVE this travel forum! Thanks to all of you for the responses; all were so helpful!

I'd like to put in a word for the Paris Visite. While not the best value for transportation, it hardly qualifies as a "total tourist rip off".
A 3 day Mobilis is 21 euro.
14 t+ tickets when bought as 1 carnet and 4 separate tickets is 21.40 euro (so that's break even for Mobilis.)
Paris Visite for 3 days is 24.80. It includes a few useful discounts. 20% at Arc de Triomphe and 20% the Army Museum make it even with Mobilis. Add 4 euro off Bateau Parisians, and you are ahead of the game.

Paris public transit is a great value, compared to NYC & London.

The Paris Pass? Now there's a total tourist rip off.

Sam,
Are you talking about the Paris Pass or the Paris Museum Pass?

The Navigo pass is so convenient. In many stations, there are turnstiles solely for the pass, so you zip through. The readers are pretty sensitive - I saw many women simply sliding their handbags over the scanner! For the tiny photo, I used my photocopier and reduced a passport photo to the needed size. And you can keep the pass for future visits. My calculation is that if I get 5 days on the pass, I save money. 4 days is about break-even, so worth it for the convenience. Take into account that if you buy a carnet of 10 tickets, you may not use them up. Or you may need to add a few individual tickets at full price.

I'm a big fan of passes in general, but adjust my enthusiasm for the specific plans that I have:
if I know I'm spending all of day two at the Louvre or somesuch, then the pass doesn't pay off price/convenience-wise.
Therefore, I tend to buy a 1-day Mobilis on mornings that I know I am going to do a lot of pinballing around throughout the day,
individual tickets or a carnet for out-and-back days, and maybe nothing for days that are out of town or lolling about in the park.

@ Kent, The Paris Pass, that's the one that includes the Visite and the Museum Pass and then marks the bundle up 50%.

Sam, thanks for the clarification on that.