I'd like to know which Centos repositories various packages are available at. Is there a directory somewhere? I tried googling it and didn't find anything.
If you have the repositories configured on your server "yum list" will show you which packages come from which repositories (or are already installed) in the third column.
[root@cobbler ~]# yum list | egrep 'foo|cobbler' cobbler.x86_64 1.6.6-1.el5 installed foomatic.x86_64 3.0.2-38.3.el5 base revisor-cobbler.noarch 22.214.171.124-3.el5 epel
yum search on the package name should show the repository from which it would install.