I'm considering a trip to Amsterdam with some friends (3-4 people) for around a week in the late spring/summer. Looking at hotel prices seems a little bit steep, and I've had success in the past in Europe with self-service apartments. The idea would be to save some money buying and cooking food ourselves while still having comfortable living accommodations. Preferably I'd like somewhere that costs less than a comparable hotel room would. Are there options for a self service-style apartment/flat in the Amsterdam area? What should I look for specifically and where?
Amsterdam, like all big cities, is expensive. Any rental apartments will be rented out to expat workers quickly, you're unlikely to find any (and they tend to be bloody expensive).
Your best bet is to find a hotel in another city and commute in by train. Leiden, Almere, maybe Amersfoort of Hilversum are all not far from Amsterdam. Leiden is a nice old city in its own right, very old university town with a rich history and lots of things to do and see, and should be cheaper than Amsterdam even considering the cost of train tickets.
Any vacation apartments in the Netherlands tend to be blocked together in self contained resort like complexes well away from major cities. There's a few on the coast, but without a car you're not going to want to stay there (plus rentals there can be more costly than a hotel room).
I used a site called Citymundo several years back - they are notable for having houseboat rentals in addition to the usual apartments. Both are rentals-by-owner, they act somewhat as an agent; you have to arrange to meet up with the owner in person when you arrive to pay and get the keys.