Fondation Louis Vuitton is the newest contemporary art space in Paris. It's privately funded and is a spectacular building that makes me imagine a sailboat in space. It's best to buy your tickets online here; the price includes admission to the adjacent park and you get to avoid the wait of over an hour on week-ends if you pre-order. There's a reduced rate of 9 Euros until December 17 as they install all the exhibits.
There are signs everywhere leading you to the Fondation, but if you are not sure just follow the crowds from metro Sablons, Bus 244, or take the 1 Euro shuttle from Place Charles de Gaulle at Avenue Friedland near the metro exit.
Just watching the water was soothing :)