A Gaelic map of Scotland has also recently been produced by Paul Kavanagh.
As well as my own work, there is also Justin Cozart's map of Cornwall in Cornish.
I have produced a set of cycling maps of Wales where I used the placenames from OpenStreetMap. My procedure was to prefer the Welsh name, i.e. use the name:cy tag where it existed, otherwise the name tag.
I couldn't actually remember how I had got the Welsh names, since they are not on the standard shapefile downloads from geofabrik.de that I usually have used.
However the full set of tags are available by using the .pbf file available at download.geofabrik.de/europe/great-britain.html which needs a little more work, firstly to convert to the full XML by osmconvert, and then to turn that into SpatialiteDB format. The tutorial here explains a little of how this is done.
This process can be horribly inefficient, since a large .pbf file is downloaded, which is processed into an even larger XML. I think there are other ways to do it which avoid this which I may look into in future.
For the Welsh names, it is necessary to look for the name and name:cy tags, and maybe also name:en tags, which exist for some places, though this is usually just a duplication of name. A very few places have an alt_name:cy tag, where there is more than one Welsh name current for a particular place.
See also WikiProject Wales on the OpenStreetMap wiki. Unfortunately neither the Welsh language OpenStreetMap rendering at http://brasskipper.org.uk/cyosm or the multilingual test page by Jochen Topf currently seem to be working.
Here are some basic renderings of placenames in QGIS, using the places.shp from the geofabrik.de shapefile of Wales, and 'joining' this to the name:cy, name:en and alt_name:cy tags from the Spatialite version.
|Holyhead. Similarly where name:cy exists, name is sometimes the English version and sometimes a bilingual form.|
|Cardiff. Many bilingual names are in evidence, the general practice here seems to be to use name:cy for the Welsh name and name for the English name, and where name:en exists, it is usually simply a duplicate of name.|
|Bridgend. The remaining two places in the populated places shapefile that have an alt_name:cy defined are here.|