So, CentOS 5.4 has been released to mirrors
So, CentOS 5.4 has been released to mirrors and will be available soon as updates to your existing systems. This ends about 6 weeks of suspended security fixes, although some security fixes were released in the CentOS 5.3 repository before the actual 5.4 release was ready.
Most of what is new can be found from my earlier RHEL5.4 release blog post.
Update: The mirrors are still not opened up yet, but you can find the ISO images torrent files from various locations.