While everyone is waiting for Firefox 3.5 (previously 3.1) to be finished, Mozilla releases a new version of 3.0 earlier then expected.

With good reasons by the way. Although Firefox 3.0.8 was planned to be released at a later time, they were forced to release it earlier. Instead 3.0.8 as planned will become 3.0.9, meaning the current 3.0.8 is similar to 3.0.7 with two security fixes. These two security fixes are marked as critical and relate to: arbitrary code execution through XUL element and XSL Transformation vulnerability.

If you're using Firefox an automatic update notice will appear (or you can select Help > Check for Updates...). You can download the stand-alone installer from Mozilla's web site.