Google Language Tools
Occasionally, I'll have need to translate text from one language to another for testing purposes. I don't do a lot of internationalization testing, but many sites today have simple text referencing an alternative language (like Spanish in the United States). For simple text conversion, I've found Google Language Tools to be quite useful. It's not going to let you take up that new project in a language you don't speak, but it might get you by in a pinch.