As part of Mozilla Firefox Project, you can download the Firefox 1.5
Beta 1 (Deer Park), which is now available.
This is the first Beta release of the next generation Firefox browser,
which would be release later this year. However, it is being made
available to Firefox's developers and testing community (thats us) for
compatibility testing and to solicit feedback.
You can download it at: http://www.mozilla.org/projects/firefox/
I LOVE this new version. At first glance there it doesn't seem new, but then you notice new things. Now you can move tabs in any order that your little heart desires. Pop-up blocker is much better (remember you occasionally got a pop-up on Firefox, now that doesn't even happen). And, it gets even better for Mac users. That's pretty much all I can tell you. Don't just take my word for it, download it.