MyMemory

This machine translation tool combines human contributions to build upon it's system, much like Google Translate has a "contribute a better translation" button after a given translation result. You can also vote and rate on translations that others have contributed. In terms of accuracy however it's not any better than the other automated translations, regardless of the fact that it uses translation memory tools. Though it seems dozens of languages are listed to be translated between each other, some popular language pairs are not supported (Japanese to English, for example). There is no way of telling which language pairs are available until you try it out.