I came across this map of language prevelance across Europe over on Wikipedia. It is interesting to see how tightly most languages actually adhere to national boundaries but periodically deviate in very drastic ways. I think the most interesting occurrences here are the pockets of Uralic variations which show up as pockets deep into Russia to the point where they compete with Altaic languages from Azerbaijan. Make sure you click through and view it in full size to appreciate the details.