Moyen Age/Cluny also features the heads of the saints which are over the door of Notre Dame. They were beheaded during the Revolution and much later discovered hidden in a garden (after the saints had already been re-headed).

I'm referring, of course, to statues....

Rodin, Picasso and Cluny. Great! places for kids too.

The one I enjoyed the most on my last trip was the Musee Nissim de Camondo.
I also recommend the Cluny, the Marmottan, the Jacquemart-Andre and the Musee de la Vie Romantique -
http://www.museums-of-paris.com/musee_fr.php?code=303
It's quite small, has a lovely garden and hosts some excellent temporary exhibitions.

The Cluny. I really enjoyed gazing at the tapestries. Also Victor Hugo's House was very interesting and free admission.

Melissa, is that you? I am planning a trip to France next year. As I was reading through some of messages in the forum I noticed this screen name. If it's you send me an email, let me know how are things with ya?

Another vote for the Rodin Museum. It's a much more intimate, get-up-close-to-the-sculptures experience than the other museums.

I love the Musee Picasso--and in such an interesting area--the Marais. Love the Marmottan, we went this year after having not been there in at least 10, the Rodin, especially in the pretty weather and one can also enjoy the garden and although not technically not museums, the Grand Palais and Petit Palais often have wonderful major art shows.

We just returned, must have crossed paths with you. In addition to the d'Orsay and Pompidou, both of which we really enjoyed, we liked the Rodin and the Museum of Natural History's Paleontology Museum. The Paleontology museum was like stepping back into the past of how natural history museums used to be (even down to the organ systems in jars of formaldehyde) - TONS of vertebrate mammal skeletons (and a couple cool dinosaurs) in two big rooms. It was lots of fun, doable in an hour, and about 5 euros for an adult. It's in the same park as the Evolutionary Museum - new and redone and supposedly really nice (but too full of schoolchildren the day we went, so we declined).

There is lots of good advice here.
I just want to put in my 2 cents -- I am a Musée Cluny & Guimet fan -- the latter has recently been totally reopened after a major [superb] renovation. It is in teresting also for the amount of Cambodian materials it has in addition to the usujal Asian culprits of Japan, China & India.