As far as immigration is concerned, one can fall under the category "kennis-migranten" (loosely translated as knowledge-workers) pretty easily, as long as the company sponsoring you is willing to pay the money, around 50K (Pay is not like the Valley, but I'm guessing this is doable).
There is the possibility of starting a company as an American citizen due to a WW2-era Dutch-American Friendship treaty (see http://www.expatlaw.nl/dutch_american_friendship_treaty.htm)
As far as startups I know of in Amsterdam, there is Fashiolista, and Sofa used to be there...