CentOS 6 isn't out yet and i needed a Red Hat 6 based system to do stuff.
I came across Scientific Linux, the name sounds kinda cheesy but don't be put off by it, there is nothing particularly scientific about this distribution other than the people who maintain it ;-) Its practically 100% Red Hat.
give it a try, its really good!
btw, i am using it with Rpmforge and Epel repositories.
http://www.scientificlinux.org/