weekends are perfect for high quality museum time:

the Frick collection (71 st st and 5 av) has long hours on fridays for free also on sundays pay as you with, the Vemeer plus other dutch painters is an amazing collection (enjoy the girl with the pearl earrings)and the breathtaking W. Turners sea storms landscapes (my fav painter btw). The Jewish museum (92 nd st and 5 av) is free on saturdays (11-5 pm) and they have a great Art Speigelman exhibition (from the little pailfacekids to the Maus to the New Yorker front), int he 1st floor. The Chagall paintings are in the second floor plus a very cool pop modern fashion expo. The short movies in the sounds expo are worth to watch too ( and only 3 min each. The MOMA ( 54st bt 6th av and 5th av) has a very cool photography expo (as always), the Magrite "wait for ever in line" exhibition on the top floor is a must! free on fridays after 4 until 8 pm. Tip: go to the top floor and then go downstairs floor by floor. The Museum of the City of New York (103 rd st and 5 th av)is free if you leave or work in the neighborhood :), if not just buy something in the shop and you will get free entrance! the central park paintings are very nice. The best now is the sandy related photography exhibition. The Whitney museum (madison and 75 th st) is pay as you wish on fridays after 6 until 9 pm. The Indiana installation/drawings is a must seen for a newyorker. And do not forget the MET, the Brooklyn museum and the National history Museum are pay as you wish!