Scientific Linux 6.0 is based on RHEL 6.0 with add-ons for scientific computing.
FWIW, the Admin tools etc. are pretty much the same as in RHEL. There is no firm date for CentOS 6.0 yet; so you if you want to see what is in RHEL 6.0 (and don't have subscription) you can try this distro to get your hands wet.
Read more at http://www.scientificlinux.org/distributions/6x/60/
I am downloading the amd64 iso.
-- Arun Khan