From the "but where is RHEL 6?" files:
Red Hat is out today with a beta release of Red Hat Enterprise Linux (RHEL) 5.3. If I'm not mistaken this should be the last major update to RHEL before the release of RHEL 6 which should come sometime in 2009. RHEL 5.3 adds a long list of enhancements to Red Hat's flagship Linux distribution.