Firefox 4.0 is the current development branch of Firefox
Firefox 3.6 (Namoroka) is based on mozilla 1.9.2
The 3.5 series of Firefox, known as Shiretoko, is the current stable branch
The GranParadiso branch containing Firefox 3.0, using Gecko 1.9
The 2.0 series of Mozilla Firefox sees various features added, and cosmetic changes.
Firefox 188.8.131.52 is now available for download.
The old stable series
Packaging for mozilla-release builds
Firefox builds from mozilla-beta
Firefox builds from the Aurora channel