I've just recently covered the Mozilla Nightly release differences:
And in there mentioned the releases known as Minefield, Gran Paradiso, and Bon Echo.
I also noted these differ from the Mozilla Release Candidates (RC) alpha and beta builds.
Well guess what? Mozilla just released a RC version of Firefox called Shiretoko.
I briefly mentioned this release back in June;
Firefox 3.1 (Shiretoko) planned features draft - Mozilla Links. It is probably right around the corner when we will be seeing the final release of Firefox 3.0. So what next? New project is to be called "Shiretoko" after the Japanese national park. Planned are a visual tab-switching feature and visual thumbnail version of list all tabs. Places might get some more improvements and some code handling refinements.
So if you are interested and want to play with this build, here are some useful resources:
Firefox 3.1 Alpha 1 now available for download - Mozilla Developer News
Shiretoko / Gecko 1.9.1 Alpha 1 introduces several new features:
First step to Firefox 3.1: Alpha 1 is here - Mozilla Links
Firefox 3.1 Alpha 1 Download - CyberNet News
Firefox 3.1 Introduces More Address Bar Improvements - CyberNet News
Want to play with it but not damage your already installed "stable" version of Firefox on Windows?
Just follow the steps referenced in this GSD post under Class Two - Home Brew to make your own "custom" standalone Firefox Shiretoko build. If you want to be even quicker, go directly to this GSD post: Build your Own: Firefox 3 (alpha/beta) Portable
Piece of cake. Then go to see what the (very little) fuss is all about.
To me Shiretoko tastes a lot like a Twinkie®; looks good and is quite comforting, but otherwise mostly just sweets for now.
Don't forget; this is "Alpha" software so I don't recommend most mortals attempt to install it as a replacement for the latest stable public release of Firefox. Your Add-on extensions will likely not work either without some hacking.