There are several options, listed below. In general, we offer
a couple of alternatives such that people can select their favourite
hotel based on budget and other criteria.

The personal preference of our host is for "Karel V", using
the cheapest room available there, because
- the quality is excellent
- it is within 5 minutes walk from SURFnet, in the city centre
- but: it is one of the more expensive options ...

All options:

http://www.karelv.nl/en

http://www.courthotel.nl/home_36.html

http://www.parkplaza.com/utrecht-hotel-nl-3531-bl/netutrec

http://www.apollohotelsresorts.com/page/hotels/apollo-hotel-utrecht-city-centre/

http://www.nh-hotels.com/nh/en/hotels/the-netherlands/utrecht/nh-centre-utrecht.html

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In addition, hotels further out include an Ibis
 http://www.booking.com/hotel/nl/ibisutrecht.html?checkin=2011-01-23;checkout=2011-01-26

and a Bastion:
 http://www.booking.com/hotel/nl/bastionutrecht.html?checkin=2011-01-23;checkout=2011-01-26

both located on a metro/tram line. But keep in mind it's definitely outside
of the city centre.

To find a lot more hotels in Utrecht, NL, try for example:

http://www.booking.com/searchresults.html?city=-2154382&checkin_monthday=23&checkin_year_month=2011-1&checkout_monthday=26&checkout_year_month=2011-1
but of course you can use any other booking web site as well.