Although many are not yet seeing the automatic update as of this post, Mozilla just pushed out the latest stable version of Firefox.
Version 3.0.6 includes a variety of stability, security and other updates and bug fixes.
A complete list of changes can be found here.
Existing users (in most areas) can now immediately access the upgrade by clicking 'Help', then 'Check for Upgrades'.
Update: The full list of platform / language versions of Firefox 3.0.6 can now be found here.