I've been wanting to make this blog multilingual for a while, and I just found a good plugin to do it.

WP_Multilingual is a multilingual plugin for WordPress. It's not an auto-translator; you have to post in each language, but those languages are tied to a single entry, and the viewer's preferred language is automatically detected using the request header. This is the ideal functionality I've been looking for.

Just one problem: Dean's FCKEditor, which you must install along with WP_Multilingual, doesn't seem to work very well with Japanese. Ugh.

Anyway, it looks fine just for internationalization. I'll look for a solution regarding the editor.