Amsterdam is a small city... you can easily walk from end to end. I stayed there for three days and felt one more day would have been sufficient. Of course, it all depends on how sidetracked you get from all of the vice and sin that Amsterdam is famous for. Definitely see the Anne Frank House, The Van Gogh Museum, and the Heineken Brewery. As far as the rest of Holland goes, I've never been, but there are lots of quintessentially Dutch things to see in the countryside.