4 days out of Amsterdam - suggestions? +Tips on good flea markets!

Towns are a good choice, you could also consider Antwerpen or Dordrecht. Maastricht is nice but takes half a day extra driving.
Or skip Leiden and add Leuven then it's a nice loop with Maastricht.
If you don't have problems with Stayokay hostels you could use some of them as accommodation. Besides cheap are some located in a nice real rural area. http://www.stayokay.nl
E.g. Dordrecht, Bergen op Zoom. Bike-rental possible in B.o.Z.
Then itinerary will be:
Haarlem-Dordrecht-(Bergen op Zoom) Brugge-Gent-Leuven-Maastricht - Schiphol
For other questions I miss the expertise.

Enkhuizen/Texel in the north, Haarlem/Leiden/Bruges ... good ideas, but you may also go the less travelled road and head to Zeeland (scroll down). Domburg, where the youth hostel is+ a castle, the ever so quaint and lovely Veere (born in the 12th century!!!), the typical and quiet town of Zierikzee on a market day, Middelburg ...

Try visiting Naarden on your way in or out of Amsterdam. It's a great little old fortified town very near to Amsterdam but hardly visited by foreign tourists.

Buy the Michelin map(s) for The Netherlands, avoid the highways and follow their "green routes". They really are very scenic.

Edited by: takeaway

If you only have 4 days in Amsterdam, I wouldn't leave the country. The Belgian cities are worth a visit, but I wouldn't combine that with Amsterdam. You could spend your entire trip in the Dutch capital, unless you really want to visit Belgium as well. (If you have to: Antwerpen is closest, easy to reach by train and a nice city to go shopping, dining, etc.)

For The Netherlands:
Utrecht is very nice and not as touristy as Amsterdam. The city has a lot of nice buildings and sights. It also has a different kind of canals than Amsterdam, you can sit at terraces of good restaurants next to the water and enjoy the scenery.
Den Haag (The Hague) is the city where the government is situated and where the queen lives. It's a beautiful town with a grand history and a lot to see. From Den Haag you can also take the tram to Scheveningen, one of the beach towns of Holland

A good way to explore Amsterdam is by boat or by bike. There are several boat companies offering tours. You may feel like the real tourist, but it's worth it! It usually takes about one hour and you will have a good first impression of the city.

You'll find a good bike rental in the Damstraat, around the corner of the Dam Square. If you want to get away from the mass tourism, the coffee shops, plastic tulips and red light district, make sure you stay away from the Dam Square and surroundings. In the Southern part of the city there's a real Dutch market, called Albert Cuyp, which is really worth a visit.

Even though you're not looking for museums, I still recommend the Anne Frank House (and there's a good pancake place around the corner). Take a d-tour to visit the "Negen Straatjes" (nine streets) with cute and strange privately owned shops. There's even a tooth brush store! I could go on and on, but just talk to locals in Amsterdam and ask them for their favourite places.

I hope you'll enjoy your trip!

...ah this is still a much beter advice than my earlier posting.
I fully agree!
Forgot the name of some design hotel in Amsterdam, aybe you know, Hester.

It would be a good idea to first read the OP's post carefully though:

We have visited Amsterdam several times and love it, but now thought it would be time to get out of the city

Den Bosch is also a worthwhile city to visit with one of the nicer churches in The Netherlands.
You can nearly always rent bicycles at train stations.

Edited by: takeaway

Oh, very sorry! I read it too quickly. -shame-on-me-

Maastricht in the south of Holland is also very nice! It's close to the Belgian border and only 1,5 to 2 hours to get from Maastricht to Brussels by car. You'll find it very different from cities in the northern part of the country. A warm, more southern atmosphere and a lot of tasty pastry ("vlaai")!

I'm also looking for suggestions for stuff to do in the Netherlands, but (and this is the hard part) I'm not interested in visiting any towns or cities.
I want outdoors stuff - animals, trees, lakes, rivers, etc. Places to walk and cycle. Accessible by public transport.
From my experiences, it seems like it's one of the least naturally beautiful countries in Europe (full of cities and industrial zones) but I'd love to be proved wrong.

I'll be based in Utrecht, for two weeks (visiting a friend), with no plans thus far.

Any response is much appreciated.

#8
You might want to have a look at this website for some ideas --> [http://www.holland.com/global/discover/countryside/active/index.jsp]