My blog (you can see the headline in my signature)support 2 language. I used polyglot, plugin for wordpress. Polyglot is easy to install, support many language but you must translate the content yourself. you can download it here wordpress have many plugin out there, check wp-plugin.net for more information. You might found the plugin you expect there.
I don't know the actual name of my translating software and looking at the finished product in another lingo was amazing. Had a Japanese lady in the uk, read some of the content and said that it did not make any sense
so get your blog tested before you go live