Paris sightseeing, transport, and tour passes. (Image courtesy of Paris Pass)
There are two main sightseeing passes in Paris:
The Paris Museum Pass (formerly known as the Carte Musées et Monuments) is one of the best deals in Europe.
It covers more than 40 major museums and monuments in Paris (plus another 21 in the surrounding region).
In addition to the big sights of Paris itself, the pass covers 21 major monuments in the surrounding region, including such big ticket (and terribly expensive) items as Versailles, Fontainebleau, and the Châteaux of Vincennes, Chantilly, Rambouillet, Mainsons-Lafitte, and more.
The pass does not cover any special exhibitions or temproary shows within the museums that have a seperate entrance fee.
With the two-day, €42 card, you'd already be saving money—and every subsequent museum or monument would be free. Plus you get all the other perks.
The best perk of the Paris Museums Pass is you get to skip the interminable lines at most sights—which at popular sights such as the Musée d'Orsay and the Louvre can last well over 30 minutes in high season. Just walk right up to a special window, flash your pass, and you're in.
An added benefit: visits are unlimited, which means you can take a monster of a museum such as the Louvre and split it up, visiting one wing each day rather than trying (and, trust me, failing) to tackle it all at once. Or you could keep going back to the Orangerie every afternoon, just to sit for an hour surrounded by 360 degrees of Monet Waterlillies in the oval basement rooms.
If you're not interested in the extras—the bus tour, the Paris Attractions Pass—you're probably better off just buying a Paris Museum Pass and a Paris Visite transport card (or individual Métro tickets) seperately.
If, however, you plan to do even a handful of those extras mentioned above—say the bus tour and, on the Paris Attractions Pass, the Seine cruise, Montparnasse Tower, and wine tasting—the Paris Pass will work out as a savings.
Do a price comparison for your planned trip to see what will be the better deal.