* create a new folder for the linguistic map (menu Add > Folder);
* list villages and towns that you know speak the language;
* look up their coordinates (where necessary) on sites like FallingRain - or better yet, record them with a GPS while you're there;
* go to them in Google Earth (you can type in
* change the icons for the placemarks if you have distinctions you want to make;
* add text to the placemarks (or folder names) in the Comments field;
* save the resulting folder as a KMZ file to be reopened in Google Earth.
Google Maps won't let you draw borders in, but (where relevant) this can be handled easily enough: File > Save Image, open it in Photoshop or GIMP, add a layer (so you can see the original at any time if you mess up), and draw the borders which, if you've plotted enough points, should be pretty obvious by then anyway. Filled in in suitable monochrome, this will look nicer in print, but has disadvantages: you lose the ability to attribute lengthy text to individual points (which shows up in Google Earth if you click on them), not to mention the ability to zoom in, or see the overall topography and environment.
By way of an example (possibly relevant to my PhD plans), here's one I did earlier: Tunisian Berber - Shilha. It has a bibliography of everything I could find on Tunisian Berber under the main folder, with works on individual villages cited under their placemarks, along with quotes on the vitality of Berber there. Berber is highly endangered in Tunisia, so I used four icons to represent different stages: a ghostly grey square for places where it disappeared shortly before 1900, a small bluish square for ones where it was still spoken in the 1930s, a white and blue circle for places where it is probably still spoken, and a larger white and blue square for places where it is still spoken by almost the whole population. It is divided into four subfolders, corresponding to different regions. As you will see, these varieties, in addition to being confined to less than thirteen villages in the whole country, are rather inadequately investigated - contrast the wealth of literature on and in Kabyle, or even Tashlhiyt. I hope this "cartographic bibliography" is found to be useful.