Thank you Gajan for info and links - very much appreciated!!!

I have a 6.5 hour transit at AMS and was wondering if it would be possible to see Anne Frank house if we take cabs both ways and buy tickets online. How long and how much would it cost by taxi?

Layover Question
 

Definitely buy online! You can bypass the (often very long) queue and enter directly via a seperate entry.

9 1/2 hrs in NBO? Where are you going to?

I've only been to Amsterdam once but my recollection was that taking the train from the airport to Amsterdam Central Station was fast and relatively inxpensive -- taking a taxi back took a long time and was very expensive.

With the train, you are at Amsterdam Central Station in 20 minutes for €4 roundtrip, I believe.
But the Anne Frank House is quite a walk from the trainstation, IIRC.

It's an easy 20 minute stroll (see Google directions: here).

You'll probably find you can do it much quicker.

Any idea how fast two US citizens can get through immigration at 8am on a Sat?

I just tried to buy tickets online and there are none available. Do they normally sell out in advance? Or if I make the trip there will I be able to get a ticket?

Anne Frank house?

Sorry, yes.

Yes, only a limited number of advance tickets are sold, and this usually means that, if your intended visit is within the next 4 weeks, all availability is gone.

You don't need to have advance tickets, though. You can line up (there is invariably a queue for walk-up tickets) but bear in mind you could be in line for up to an hour before you get inside.

If you don't fancy waiting, there are lots of other things to do. Just stroll around the city, visit any of the other museums (the Royal Palace on Dam Square is not far from either Amsterdam Centraal, or from the Anne Frank Huis) and would easily take up an hour or so of your time.