Firefox 3 beta 5 is already here

Acid3 - 69/100
Javascript is now significantly faster.
In addition, we have a slightly hacked-in interface (for WindowsXP).

As always, beta can be downloaded at http://www.mozilla.com/firefox/all-beta.html

[UPD:]
Some (many) extensions were disabled due to compatibility checks . This does not mean that they are not functional. :)

To disable the verification, go to the address about: config and add the extensions.checkCompatibility boolean parameter with the value false

[UPD:]
http://ftp.mozilla.org/pub/mozilla.org/firefox/nightly/ - nightly builds

Firefox 3b5 Portable from PortableApps