Actually there seems to be a pattern, but there is a version number at the end which doesn't fit in anywhere.

> http://yum.postgresql.org/9.3/redhat/rhel-6-x86_64/pgdg-redhat93-9.3-1.noarch.rpm
> http://yum.postgresql.org/9.2/redhat/rhel-6-x86_64/pgdg-redhat92-9.2-7.noarch.rpm
> http://yum.postgresql.org/9.1/redhat/rhel-6-x86_64/pgdg-redhat91-9.1-5.noarch.rpm

So we either need a list of URLs, one for each version, or include our own .repo file. I prefer using the provided rpm (so we need a list of URLs) because it's possible that they will make changes to it (so just yum update and we will have the updated version). The drawback is, of course, we need to add a URL for each new version that we use. How about that?