A Danish chap from microformats.dk has recently converted the 11 national bicycle routes - 4,233 km in all - from GPX to KML files which can be added to the Google Earth program. So if you're planning a cycle holiday in Denmark, this is a cool way to start researching the routes.
Vestkystruten [West Coast Route] 560 km – 70 % paved
Hanstholm – København [Hanstholm - Copenhagen] 420 km – 80 % paved
Hærvejsruten [Army Way Route]450 km – 78 % paved
Søndervig – København [Søndervig -Copenhagen] 310 km – 90 % paved
Østkystruten [East Coast Route] 650 km – 90 % paved
Esbjerg – København [Esbjerg - Copenhagen] 330 km – 92 % paved
Sjællands Odde – Rødby Harbour 240 km – 90 % paved
Sydhavsruten [Southern Ocean Route] 360 km – 95 % paved
Helsingør – Gedser 290 km – 92 % paved
Bornholm 105 km – 90 % paved
Limfjords Route 610 km – 90 % paved
All 11 cycle routes in a zip file (471 KB)
To read more about each route Visit Denmark has some descriptions here.
There are 11,000 km of signposted bicycle routes in Denmark. Apart from the national routes there are regional and local. Some of the national routes are a part of the impressive Euro Velo network of 66,000 km of cycle routes around Europe. Still a work in progress, the Euro Velo network is up and running in some regions.
For example, The North Sea Cycle Route features 6000 km of signposted cycle routes through seven countries on it's circular route of the North Sea. The world's longest signposted international cycle route, apparently.
If you're going to warm up with a Danish cycling holiday, printed maps of the Danish cycle network are available from the Danish Cyclists Federation.
Visit Denmark also has a magazine called Pedal, in English, which is viewable online and is all about cycling holidays in this country, including information about the quality label - a logo to look for to recognize shops and accomodation that caters to cycling holidaymakers.