It is winter in the northern hemisphere - so it is time to map winter sport trails.
The project OpenPisteMap defines all features you need, but it only renders alpine ski features. Therefore I started my project XC Ski Trail Map.
It visualize all ways and relations with the piste:type=nordic tag as a vector overlay with OpenLaysers.
I use Googles Terrain Map as standard backgroud, because we do not have such light map with hillshading now. But you may switch to OSM-maps (without terrain)

Website (english): http://osm.virtuelle-loipe.de/loipemap
Wiki (only german yet): osm.wiki/User:Langl%C3%A4ufer/Loipemap

In the wiki you find hint for tagging xc-ski trail - I used the features from PisteMap combined with some general tags and a bit from hikingmap.

The ways a tagged for modelling the physical way. (this is also rendered in Osmarender)

way:
piste:type=nordic

Relations are used for (marked) courses. (this is not a collection it is like a bicycle route - you may want to follow the whole track)

relation:
type=route
route=ski
piste:type=nordic