Almost two months after RHEL5.4, Centos 5.4 was released on the 21st October. This version includes various changes into the virtualization field and it includes support for KVM (kernel-based virtual machine) hypervisor and the Xen hypervisor.
Also this release features many bug fixes and security updates, and should be an easy upgrade for users running centos5.x: yum update
For the full list of packages changed/added please see the centos5.4 release notes: http://wiki.centos.org/Manuals/ReleaseNotes/CentOS5.4
