Last time I was in Alkmaar (a day trip from Haarlem, where I was staying), I stopped by this place for a beer and picked up their business card:
http://www.stadenland.com/
At €52.50 for a single room, you'd be hard pressed to find better than that. It's near the station, obviously given the address (Stationsweg 92-94), about 15 - 20 mins walk from the City Centre / Achterdam / Biermuseum. You can save a few Euros by booking through hotels.nl who don't charge a fee (I've booked through them before elsewhere):
http://www.hotels.nl/alkmaar/stadenland/
The only thing, it is above a bar so it may well be noisy. If anyone does try it out, please leave a report.
Alkmaar is a great place. You can sit outside on the terrace of the Biermuseum by the canal and watch the world go by and you are only a minute's stroll from the Achterdam.
Cheers
Moondog