As part of the danish government open data strategy the Danish Geodata Agency offering a WMS free service of their aerial imagery. License (link goes to a danish page)
To use in different OpenStreetMap editors Gregers Petesen have setup a mapproxy.
JOSM editor (Note use add TMS)
Coverage and age 100 % coverage of Denmark (43.094 km2) and in 10 cm resolution. Age spring 2012 and some parts of Denmark from spring 2013.
More about the mapproxy setup (text in danish)