EDIT: This is an old post. Be sure to check out the new post for the Release Candidate version
If you are looking for the direct links to download Red Hat Enterprise Linux 7 Beta here you have the links hosted by the upstream vendor itself.
As the vendor highlights here I assume that you have the appropriate subscription
If you plan to use the network install iso (first download link) you should be pointing to this url as your installation source:
And here the Red Hat Enterprise Linux 7.0 Beta Installation Guide
PS: I personally still have to make up my mind about CentOS joining Red Hat announcement