Unofficial Google Translate Firefox Extension (see descrip)

http://blog.jimmyr.com/Unofficial_Google_Translate_Firefox_Extension_05_2008.phpDirect Link
http://www.jimmyr.com/google_translate.xpi

FORGOT TO MENTION
1. The translation is automatically copied to clipboard.
2. You can also select text in search boxes or text areas (like the youtube comment box) and alt click the selected text.
If you want to translate custom stuff you cango directly to
http://translate.google.com/translate_t

If it doesn't let you download it try this:
http://www.buildquiz.com/google_translate.zip

Unzip it and then drag and drop google_translate.xpi into firefox.