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): http://wiki.openstreetmap.org/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

I found some vandalism (imaginary objects like motorways, airport in Sineu, rails, POIs, ...) of user sergiclar on Mallorca. Mostly affected was Sineu but also Inca, Palma, Son Serva.

http://www.openstreetmap.org/user/sergiclar/edits
I hope I removed the most.

In the last month I developed two tools for inspecting osm data.

First tool is the Restriction Analyser. It checks (syntax and directions) of turn-based restrictions and visualize them on OSM.
Note: At the moment it can't handle restrictions with more or less than one via nodes.

Link: http://osm.virtuelle-loipe.de/restrictions/

Second tool is the OSM History Browser. It allows you to browse the history (like history in the wiki) of each node, way or relation and to see the difference between two versions of the object (like the diff in the wiki).
Note: you have to put in an id of the node way or relation.

Example: http://osm.virtuelle-loipe.de/history/?type=relation&ref=33333

What happend to the edit option of the gps traces?
The first time I used it, the map zoom to the track in edit mode and the whole track was shown in the map.
Since some days when i use the edit option of a track, the map centers in the pacific ocean and no track is displayed.
This is not a problem of my tracks, I tried it already with tracks form others.
The tacks in the database work fine.