The Park of flowers (Keukenhof) this is the bigest garden of flowers in the world (tulips and other), and most photographed place in the world. Entrance ticket 16,5 USD = 14. EUR the official website www.keukenhof.nl
Boat tour on the canals of Amsterdam is 11,8 - 14,2 USD = 10 - 12 EUR (about an hour) the web site of a company www.lovers.nl
Provides free access to some of the museums of Amsterdam (more than 30), travel on public transport and channels cruises, as well as discounts for parking and even some more discounts, more on official site www.amsterdam.info/pass/
In the Netherlands soft drugs are officially resolved. It is officially authorized to smoke in kofeshopes. In ofeshop present a menu with different types of marijuana and hashish. The bartender can advise you and help you in your choice. You can ask something lite. Or something a little stronger.
Officially mushrooms in the Netherlands aren't resolved,it is possible to by it in specialized shops. The detailed instruction on application, here is examples of the prices for 100 gr.