The final build comes on next Tuesday. This guide covers the major stuff that has changed with FF3.
dria.org » Blog Archive » Field Guide to Firefox 3
We’re done. Firefox 3 is going to be launched very soon. In anticipation of this long-awaited event, the folks in the Mozilla community have been writing extensively about the new and improved features you’ll see in the browser. The new features cover the full range from huge and game-changing to ones so subtle you may not notice them until you realize that using Firefox is just somehow easier and better. The range of improved features is similar  whole back-end systems have been rebuilt from scratch, while other features have been tweaked slightly or redesigned in small ways. Overall the result is the fastest, safest, slimmest, and easiest to use version of Firefox yet. We hope you like it.
dria.org » Blog Archive » Field Guide to Firefox 3