The official North Sea Cycle website is a good starting point for information about this route. It is not perfect but has some useful features and a Riders Comments page where you can ask questions and share experiences.
I discovered the Cycletourer website when we were planning our first ever cycle tour in 2005. We did the NSCR in Norway and the Cycletourer site has useful information about cycling in Scandinavia and some travel reports with nice pictures. It was also the first site that gave us and inkling of what cycle tours were all about.
I bumped into the Bliss on Wheels site purely because the author had read my NSCR Norway travelogue and enjoyed it. I am not sure quite how we missed it in 2005 and 2006 whilst searching for information about cycling in Norway. The webmaster Jerry has lots of useful and interesting information including cycling with folding bikes (something we have just started). There is also a travelogue about cycling in Northern Norway which I have to read fully at some point. This is one of the places we would like to go for our summer 2008 (or earlier if circumstances permit).
Another site we found in 2005 was the Bike Norway one. This is the starting point for cycle tourism in Norway with information about the official signposted routes.
Information : Places to buy maps and guides and gear. We used the Fietsvakantiewinkel to buy maps for the NSCR Norway, Denmark, Germany and the Numedalsruta and Rallarvegen in Norway. Sadly they no longer have shop in Woerden (a nice twenty kilometers cycle from here) but they continue to sell maps and guides via their (Dutch language) webshop.
We have bought some road maps from Bever outdoor sports shop. They have a good range of road maps and travel guides in stock. As well as Dutch language and culture guides they stock English language guides such as Lonely Planet and the Rough Guide series.
Information : Places to buy gear.Our local bike shop is SNEL who are renowned for their touring bikes. We have bought most of our Ortlieb bags there and other useful bits and pieces.
We've bought stuff from Bever (see above) such as our Trangia cookers and the relatively lightweight Moonshadow Duo tent. A fun place to wander round, and very tempting to pick up just another essential oojamaflip for the next cycle tour.
Another outdoor shop we like and equally dangerous for one's bank balance is Zwerfkei based in Woerden. We bought both our Macpac and our MSR winter tent from there.