I'm going to the Netherlands this summer as well. I thought of planning my way through but I think I'll just head on north from Maastricht until I find some water :-)
Then maybe go left to the polders and Amsterdam, and go back in the general direction of Antwerp/Belgian Limburg (or maybe head to East Flanders and the Belgian coast, who knows). I thought that if I plan this trip too much, there won't be much space left for adventure.
I thought of taking the natural campsite pass to sleep around in the country. Has any of you used that in a previous trip?
Home - Stichting Natuurkampeerterreinen
It looks nice on paper, but I'm afraid of it being too crowded.
I also heard of hard-to-locate wild camping sites, I guess it's worth a try.