The Paris Museum Pass???

You can find the details at the official site of the Paris Museum Pass. They can be purchased for 2, 4, and 6 consecutive days. A list of prices and what it covers are listed, as well as some examples of individual ticket prices. Basically, if you visit 4 museums/monuments with the two-day pass, 6 with the 4 day pass, and 8 with the 6 day pass, it will pay for itself. But probably the BIGGEST benefit is that it will allow you to bypass the lines at most of the sites....extraordinarily valuable!

The Paris Museum Pass lets you bypass the long lines, EVEN ON DAYS WHEN THERE IS FREE ADMISSION. If you happen to be at a museum when there is a free day, you may not be saving anything that day but you can still avoid standing in the extremely long line. Go up to the door and show them your pass!

Let me re-emphasize... the biggest value of the Museum Pass is in time saved. The longest line at most of the museums and monuments is not the entrance queue, but the ticket line. On busy days at the bigger attractions, you can save up to a hour of time by using the pass.

The only major attractions the pass doesn't cover- the Eifel Tower, and Notre Dame (admission is free, anyway). The Tower of Notre Dame is covered, but you can't skip the ticket queue.

Another huge advantage to the PMP is psychological. You don't agonize over whether an attraction is worth the entrance fee and you don't feel you've wasted money if the attraction isn't interesting to you or if you only have a short time to see it. You might just find a personal "gem" that you wouldn't have even thought about.

The only downside is that the PMP is valid for consecutive days.

Before I go to Paris, I make a list of all the things that interest me and organize it by area (usually by arrondissement, which is simplest). Then wherever I happen to end up on a given day, I have a short list of what's there.

Most museums and monuments are closed one day a week - best to make a note of those days for any sights that are on your A-list.