With Firefox 3 out of the beta testing phase, Mozilla has released Mozilla Firefox 3 RC1, as it nears it's official June 2008 launch date. With the release candidate, it is going to be very similar to the final version that will be released soon.
You can grab Mozilla Firefox 3 RC1 here: http://releases.mozilla.org/pub/mozilla.org/firefox/releases/3.0rc1/win32/en-US/