PDOK (Publieke Dienstverlening Op de Kaart) is the Dutch National SDI that provides many free maps and other geospatial services like WFS and an address-finder. Thijs Brentjens has provided a Heron app that allows viewing these services. Click on the preview image below or go directly to the demo at: nieuwsinkaart.nl/pdok.
More info on PDOK can be found at pdok.nl.