The MLA has just opened up a site where you can "[v]iew an interactive map showing the density of speakers of thirty-seven languages and language groups", with all kinds of neat features, based on the 2000 census data. The site is pretty heavily loaded, so you might have to wait a while to see your maps, until the rush dies down.
From my own experiences, I surmise that they are not caching maps, even common ones like "English by county for the mainland U.S." As a simple sample, here's a map of the "density" of Armenian speakers by county for the mainland:
[Update: as reader Margaret S. emailed to point out, this is an odd use of the term "density", since it refers to the number of speakers per geographic region (county or zip code) for regions that are highly non-uniform, both in size and in population. It would be nice to be able to see some alternative normalizations, say proportion of the local population, or speakers per unit area -- and perhaps the MLA site should refer to what they now show as "the population of X speakers by county (or by zip code)", or "the number of X speakers ...", rather than the "density of ..."
Whatever the nomenclature, here's a map of the number of Chinese speakers per zip code for the region between Philadelphia and New York:
]Posted by Mark Liberman at June 16, 2004 08:41 PM