What are fun things to do in Amsterdam?

Someone i know is going and i want to help them find things to do if they don't already have an itinerary or w/e

It all depends on what you like, really.

There are lots of museums, such as the Van Gogh Museum, The Rijksmuseum, but also a sexmuseum and a beer museum.

There is a lot to be seen if you are interested in Architecture.

You can take a canal boat ride, you can rent a bike and try to survive the traffic, you can take a trip from Amsterdam to places like Volendam, Enkhuizen, Zaanse Schans.

Of course you can visit a coffeeshop, if you are so inclined, or wander around the Red Light District.

So - give a bit more detail about what interests there are - so you can get a more specific answer.

U_S_S_Enterprise gave you some good pointers already, you can find much more detailed info, also on what he told about, on this site:
http://www.amsterdam.info/

I like just to walk through town on a nice day, see the different parts, and sit down in a nice brown cafe, you will find them on almost every second corner in a big part of town, and have a warm drink.

deep sea diving, rock climbing, house burning, cliff diving u know the normal stuff or u could get a litle crazy and go to museums thats only if u have enough courage, or if ur lucky u might be able to see the sun i hear it gets dark at late ninghts