Upgrade to CentOS 5.8
CentOS 5.8 has been released within the last 24 hours :)
To update your existing CentOS 5.x to CentOS 5.8, simply run the following command:
Ensure that you have only standard CentOS repositories enabled to avoid dependency issues.
If you are unsure, you can check what version of CentOS you have installed here.
For new installations, you can download the CentOS 5.8 32-bit or 64-bit ISO from here: http://isoredirect.centos.org/centos/5/isos/
Browser over to http://wiki.centos.org/Manuals/ReleaseNotes/CentOS5.8 for CentOS 5.8 release notes.