I have a 5 1/2 hour layover in Amsterdam in October on my way to the U.S. Is that enough time to take a quick trip into town and just see a little of the city?

I know the city is close but knowing how long security can be to get on a flight to the US I would be hesitant to risk it. I think you would end up with only an hour or so there when you allow for wheel down to get out to transit, getting into the city, getting back from the city and checking in to the US flight 2 hours in advance.

I usually fly through Amsterdam, and would agree with nytraveler that going out in the city is a bad idea with only 5 1/2 hour layover.

Not enough time. Fortunately it's a fairly interesting airport.

We were at the airport in Oct 2009 and they had some paintings from the Rijksmuseum, you may want to check and see how the restoration project is going. Otherwise like suze said, it's an fairly interesting airport, as airports go.

If you really want to see Amsterdam, you can do it. I've done it without a glitch. The train station is directly under the airport and technically Schiphol airport strives to enable passengers to leave the airport within 20 minutes after landing. Unlike Frankfurt airport, Schiphol is well designed so it's not that far of a walk to get to the train. They have a train leaving for Amsterdam every 10 minutes. I was on the train to Amsterdam 25 minutes after my plane had landed and it took about 20 minutes to arrive in Amsterdam. I actually got to spend a bit over 3 hours in Amsterdam and left the Amsterdam Centraal train station 90 minutes before my flight departure time. I arrived at Schiphol slightly over one hour before my plane departure time and that was plenty of time since I already had my boarding pass with me. It was a fun layover because I had a chance to hang out with a relative who lives in Amsterdam and bought all my favorite Dutch food supplies to take home.

On another trip I actually stayed in the airport for the entire 5 1/2 hours because it was bitter cold outside, it was incredibly boring and punishing to stay inside Schiphol for that long.

It depends. Your plane can take a long time to taxi to the terminal -arrival time is the time it touches down not when it gets to the terminal. You may get lucky and get through quickly. If you have euro coins you can buy a return ticket to Amsterdam at a machine and get the train in.
However for a flight to the US the gate closes early as all security and questioning is done at the gate. So you need to be at the gate at least an hour before your flight leaves.

So in theory you have maybe 3 hours in Amsterdam. Whether it is worth the risk and the stress only you know. It only takes a missed train or a problem on the trains to screw things up for you. A taxi would be no quicker, and a lot more expensive btw.

You can go up to the viewing terrace at Schiphol if you want some fresh (well fairly fresh) air, and watch the planes there for a while if it is reasonable weather. You do go through passport control for that. There is also a good set of shops land side of passport control if you want something different, a change of scene from air side terminal, though they of course don't sell dutyfree.

The Rijksmuseum has a small display there and there is now the Schiphol library for people on long layovers. You can't take the book with you but you can borrow one and read there, or download an e-book if you want. They also have papers and magazines to read there.

I think this question has to do more with your tolerance level for stress. Some people have no problem doing something like this & could easily fit in an hour or two in the city. For me I would be so worried about making my next flight, I'd be having an anxiety attack, and not really able to enjoy my time out of the aiport.

Have the same situation this winter. Decided to spend the night in Amsterdam and fly out the next day.