The World Atlas of Language Structures, in preparation, “will show structural features of languages in much the same way as linguistic data are displayed in dialect atlases.” I’ve seen German dialect atlases that show how words change from place to place; what they’re talking about is linguistic structures — for example, whether adjectives precede or follow nouns — which is more fundamental. The maps (1, 2) on the site are fairly rudimentary; I hope the final product is much more cartographically interesting. The Guardian has more; via Languagehat.