I found this offer in a newspaper the other day and was curious to see if anyone had posted it on FT yet. Sure enough, it's here! ^
By the way, for those who haven't yet clicked on the link provided by the OP, the museums on offer aren't just little obscure ones; they include such well-known institutions as the Guggenheim, the Jewish Museum, and the Brooklyn Botanic Garden (all in NYC), the Fine Arts Museum and the Isabella Stewart Gardner Museum (both in Boston), and the Philadelphia Museum of Art.
Just as one example, normal adult admission to the Guggenheim is $18 each. You can save $36 on this visit alone!
Fortuitously, I have a trip to NYC coming up tomorrow, and some spare time to visit museums....