We are traveling to Amsterdam in early August (2014). I would like to purchase the musemkaart card before we arrive. However, the website indicates the card only available to Netherlands residents on line and the site is only in Dutch. Any suggestions?
Maybe ask your hotel to buy them for you?
There is no need to purchase the card in advance, as it's sold at the participating museums. Dutch residents get it a bit cheaper, but it's still a great deal if you are seeing a fair number of museums, particularly as it covers places in the whole country, not just Amsterdam. As promised in Rick's book, I found that the Amsterdam Museum had no line at the ticket desk, so it was a good place to buy the card (I also really liked the museum).
I can't think of any case where you benefit by buying a city-wide museum pass before you arrive in that city.