Paris Visite

The Paris Convention and Visitors Office offers online purchasing of museum and transit packages. Their Paris Visite page offers a 5-day transportation pass for 29.90 euros ($40). The pass allows unlimited travel on the bus, metro, tramway and RER networks in Paris and its suburbs (Zones 1-3). One can purchase it online (although I'm not sure how it is sent to you). A single metro ticket costs €1.60, and can be used for one journey, including all connections. This ticket, valid for zones 1 and 2, allows you to travel anywhere in Paris. On the buses, you use the same tickets as in the metro, with no limit of distance (including suburbs), except on the Balabus, Noctilien and routes 221, 297, 299, 350 and 351. But on the bus, your ticket is only valid for a single journey, with no connections. Looks like it would be simpler to just get the Paris Visite pass, even if we don't use $40 worth, since it covers the whole public transport network (metro, RER, bus, tram, suburban train, Montmartre funicular). These travel passes can be purchased in main metro and RER stations, in SNCF train stations in Ile-de-France and in Paris airports. Certain passes are also available at the Paris Convention and Visitors Bureau.
AND THE TRAVEL PASS MUST NOT BE PUNCHED IN THE MACHINES ON THE BUSES. JUST SHOW YOUR CARD TO THE DRIVER AS YOU GET ON.