CentOS 6.3 32 bit minimal install ISO
http://mirror.wiredtree.com/centos/6/isos/i386/CentOS-6.3-i386-minimal.iso
CentOS 6.3 64 bit minimal install ISO
http://mirror.wiredtree.com/centos/6/isos/x86_64/CentOS-6.3-x86_64-minimal.iso
Good mirror site for all CentOS ISO images
http://mirror.wiredtree.com/centos/
http://archive.kernel.org/centos-vault/