You can either download the Noodle Firefox extension from the Mozilla Addons Site (recommended but requires registration) or below.
Noodle Firefox extension [1.0.5].
If you download from the Mozilla site, you can leave a review and increase the chance it'll get accepted into the public area (no registration required).
It has been tested with Firefox 2 and 3. Surprisingly, it also works fine with both of them, too.