We have a four hour layover at the airport in Amsterdam. Is this enough time to leave the airport? We would like to see some tulips if possible. Are there tours available from the airport? Would it be too expensive to have a taxi take us on a two hour tour? This would be my first time in Amsterdam.

Your 4 hours is really not (4 hours). Depending if your flight gets in on time, and if it takes you 1/2 hour+ to exit the airport, AND you need to check back in for your next flight 1-2 hours prior. Certainly possible to hire a taxi for an hour, but into Amsterdam itself is maybe 20 mins. drive from the airport.

Hopefully someone will have information of tours leaving/returning from the airport (though I have never seen that posted, and I've seen this A'dam layover question asked alot).

If you have 6-8 hours we'd send you via taxi to take a canal boat tour and have lunch.

Four hours is definitely pushing it. Schiphol is a very efficient airport and immigration processing is very quick, so it might be possible. The trains into the city are frequent (every 8 minutes or so), cheap (about 4 euro) and quick (about 20 minutes), so you might be able to zip into the center city, visit the floating flower market and zip back to Schiphol.

<This would be my first time in Amsterdam.> What do you expect to having seen in an hours time? ... considering your flight arrives in time, immigration goes fast and knowing that Schiphol requires a 2 hour check-in time!
Why not just relax, walk around the shops in the airport and have a few drinks.

If you arrive on time and immigration is not too slow, consider taking the train into Amsterdam. It is risky though. Last week Central Station was closed for hours due to a bomb threat. And Schiphol is a very good airport; there's even a small Rijksmuseum there.

I had a 4 hour layover in Amsterdam 2 weeks ago, and didn't feel a need to leave Schiphol at all. There are lots to do in the airport, the museums, shops, walking around and exploring, it really does pass the time real fast. Just so you know 1-I'm not much of a shopper, 2-I work for a museum, so the last thing I want to do is visit a museum during my break. However, I did both window shopping and museum visiting, and ironically, didn't have enough time for the museum as thoroughly as I'd wanted!!! Of course, if you want to go out and visit Amsterdam, by all means, I think it would be fun, and it's a beautiful time of year to do it. I just didn't feel like lugging my luggage to a baggage check, and then go claim it before my flight.