The Ubuntu project has released Hardy Heron 8.04.1, as the release number implies, it is a bugfix release which contains all the security updates and bug fixes for the last 2 months since the first release of 8.04. The release can be downloaded from Ubunty Hardy download page in the form of ISO files.
Current users need not to download the new CD as they are most likely have all the security patches applied via the built-in Automatic Update feature in Ubuntu.
As a bonus, the CD also includes the production release of Mozilla Firefox 3.0 compared to 3.0 Beta in 8.04.