I just found a Chrome extension that translates between different languages. See what you think:

https://chrome.google.com/extensions/detail/jlhlebbhengjlhmcjebbkambaekglhkf

Or simply go to the Chrome Extensions site and search for "Bubble Translate."

Basically, it can translate highlighted text or the whole page. There's also a real-time translator that immediately translates what you type. Additionally, it detects the web page's language, and you can set up automatic translation for specific sites if you want. The translation is based on Google Translate ( http://translate.google.com/ ) so you can see for yourself how accurate that is. As far as what it's trying to do, it doesn't seem too bad.

It's not the same idea as the Firefox plugin you're talking about, though. I wouldn't mind helping to develop the Chrome version.