The World Atlas of Language Structures (WALS)

is a large database of structural (phonological, grammatical, lexical) properties of languages gathered from descriptive materials (such as reference grammars) by a team of more than 40 authors (many of them the leading authorities on the subject).

It also consists of

of 141 maps with accompanying texts on diverse features (such as vowel inventory size, noun-genitive order, passive constructions, and “hand”/”arm” polysemy), each of which is the responsibility of a single author (or team of authors). Each map shows between 120 and 1370 languages, each language being represented by a symbol, and different symbols showing different values of the feature. Altogether 2,650 languages are shown on the maps, and more than 58,000 datapoints give information on features in particular languages.

And it is available online for free! Kudos to the linguists!

Via: Open Access News