There are so may museums in Paris that you could spend weeks and not see them all, whether free or for a fee. We love the Gustav Moreau. The day we went it was free but the admission is so small it's worth the price.

Another we loved , even though neither of us is a great fan of modern art is the Musee de Art moderne at the palais de Tokyo. The building itself is wonderful the view from the terrace over the Seine is great and we didn't even mind most of the exhibits. Good cafe too

Ms. Bear and I visited the Musee d'Art Moderne last week. Unfortunately they were installing new exhibits in two of the major galleries, so only two (or three) smaller rooms were open. I believe they were arranging the new exhibits in time for the "free museum night" tonight (Saturday night, Paris time) or for Sunday, so it should not be a problem after that.

Just back from Paris. Loved the Petit Palais and Carnavalet. And although I had reservations about the crowds at the Louvre (never visited although this was my 3rd trip to Paris), we visited on a Wednesday night after 7 pm, got in without waiting, and had many rooms all to ourselves. I was VERY impressed with the Louvre.