If the Louve is too daunting for you, or if you are just short of time, then the Orangerie is your best bet for a quick, quality art hit. Located at the far end of Jardin des Tuileries, this is a beautiful experience. At entrance level there are two perpose built oval rooms that house Monet's Decoration des Nympheas.
Displayed in diffused natural light, you could spend a whole day sitting and pondering these works.
On the lower level is the collection of Paul Guillaume, a fantastic survey of early 20th century art, including,