CentOS-6.1 is based on the upstream release EL 6.1 and includes
packages from all variants. All upstream repositories have been combined into one, to make it easier for end users to work with.
There are some important changes to this release compared with the previous versions of CentOS and we highly recommend reading this announcement along with the Release Notes.
Since upstream has a 6.2 version already released, we will be using a Continuous Release repository for 6.1 to bring all 6.2 and post 6.2 security updates to all 6.1 users, till such time as CentOS-6.2 is released itself.
There is also a minimal install CD that will get you a very small base install that you can add to.
And now: Have fun.