The language learning website, italki.com, has been around as a social networking site since 2006. Starting in April, they decided to develop a new version of italki: italki Knowledge. italki Knowledge is made up of a bunch of wikis functioning as open textbooks—free for anyone to access and edit. The wikis span a multitude of languages, learnable in almost as many (you can learn Korean using German, Spanish using Mandarin, vice versa and more). The Wired Campus reports that the site really only took off this month, so make sure to check it out and contribute if you can.
All wiki pages are dedicated to the public domain using the Creative Commons Public Domain Dedication.