Siri is more powerful than Apple lets on so it's up to the tweaking, hacking, tinkerish souls of the jailbreak community to unleash her full potential. Like this latest Siri hack, Lingual. It's a jailbreak-only tweak that turns Siri into a translation device. Just say what you want to Siri, name the language you want to translate it to and Siri will display it in its translated glory.
Lingual pulls in its results from Microsoft Bing's Translate API and supports up to 30 different languages which is plenty good. I do wish Siri whispered back the translation to me instead of just displaying it, though. [Assistant Extensions via The Verge]