The lounges are usually run by the different airlines, some airlines do offer use of the lounges on a one time basis, for a price of course. Check with your airline to see if they offer lounge access. Also, most airports have private lounges not affiliated with airlines that passengers can use between flights, Schipol is no exception and does have a private pay lounge that is available to anyone that wants to pay the fee:
http://www.trip-extras.com/netherlands/amsterdam/amsterdam-schiphol-airport/airport-lounges