MajorGeeks.com has a 3.0.1 release of Firefox, but the Firefox/Mozilla website doesn’t have the release notes updated for it.
http://www.majorgeeks.com/Mozilla_Firefox_d2248.html
Apparently there were only security issues addressed, the same ones as for Firefox 2:
http://www.mozilla.org/security/known-vulnerabilities/#firefox2.0.0.16
http://www.mozilla.org/security/known-vulnerabilities/firefox30.html