The new version, Firefox 3.0.11, addresses several security and stability issues. Release notes can be found here.
A few bugs were repaired as well.
If you haven't been offered the automatic upgrade yet, just tap on 'Help' at the top of the browser, the 'Check for Updates' and follow the prompts.
All language downloads can now be found on this page along with versions for Windows, Linux and Max OS X.
Update July 21, 2003 - Firefox 3.0 has moved to version 3.0.12. Users that have opted to stay with the 3.0 series rather than move to 3.5.1 should download this security update.