The next version of Mozilla's web browser, Firefox 6, will be officially released on Tuesday, August 16. There are no major UI changes; most of the other changes are under the hood. That's a welcome upgrade as Firefox 6 is reportedly 20% faster than Firefox 5. Also, while Firefox 6 does offer full screen support, it's not Lion-native fullscreen support, which is somewhat of a disappointment.
For those of you who don't want to wait till Tuesday, you can actually download the final release of Firefox 6.0 here from Mozilla's FTP servers.