The orginal Grasshopper (the one at the nieuwezijds voorburgwal 59) is a nice coffeeshop
where it's also possible to eat lunch. They sell muffins en coffee with grass inside, you must give it a try. The atmosphere is friendly and the interior isn't to dark. Prices are abit high but the quality is ok.
The Grasshopper (the one at the Oudebrugsteeg 16, close to the Red Light District) is located in a large historic building. In the basement you will find the actual coffeeshop, this is where you can buy your grass or hash from the 'house' dealer. The quality is good but prices are high. Outside there's a terras with a nice view on the channels and the central station, an excellent spot to relax. On the ground level there's a bar and during the afternoon/evening a DJ will play music there, the next level has another bar and at the top there's a restaurant. The atmosphere is good but many people either love or hate this coffeeshop.