If you're interested in the properties and structural diversity of languages, you're in luck. A new edition of a print reference has moved online, and is freely available. The World Atlas of Language Structures Online (or WALS Online) offers 141 maps, detailing information about a total of 2,650 languages.
Our print edition resides in MSEL's General Reference Collection at P143.W67 2005 Quarto. We do have a catalog record for the online edition, also.
I love seeing reference works move online, especially when that means you can interact with the information. The maps in WALS Online let you zoom in and out, click on data points for more information, and alter the map legends. If you want to use or re-use this digital information in some fashion, please read the information they provide on the Creative Commons license and the Google maps guidelines. WALS Online also gives you information about how to cite the information they provide.