We have set up (Stefan actually) fantastic facility to help you to help us translate SIPE to your native language - Transifex.net. The first fruits of that are complete localizations to Polish, Russian. We also have full translations to Chinese, German. Italian, Finnish, Danish have been also updated through the site. It's so easy now to translate string by string using convenient web interface.
Our translation page is here:
Visit, help translate to your language.