Nederland Fietsland is a website where you can find local and long-distance bicycle routes in the Netherlands.
There are 2 main types of (sign-posted) bicycle routes in the Netherlands:
1. Bicycle junction routes ('Knooppunten-routes')
These are more local, shorter routes. The junctions have numbers, and you cycle from number to number. Often, at the junction points there are boards with overview maps.
There are no real junction routes within Amsterdam, but outside the city boundaries there is a dense network of routes. Amsterdam is not very big, so getting outside of it is easy.
2. Long-distance routes (LF-routes)
There is a network of about 30 LF-routes all over the country. They are designed for multi-day trips, along pleasant, scenic and quiet bicycle routes.
This website includes gpx files of all LF-routes, for those who cycle with GPS navigation devices.
The website has a recreational bicycle route planner (also in English).
This (English language) online film gives some further insight in the cycle junction network.
Tree lane with cyclist