WordPress.org

How it's work? Just install the plugin and active it. Once done, just click on any post you want on your blog for translate it. We just add a few language:French, Italian,Spain,German and Japanese. We will provide more language and more feat on the next version.

You can see an exemple here : http://wordpress.devoox.net/ On that exemple, the text is in French and you can double click in for translate it.