rpmforge:

rpm -ivh http://pkgs.repoforge.org/rpmforge-release/rpmforge-release-0.5.2-2.el6.rf.i686.rpm

epel:

rpm -ivh http://dl.fedoraproject.org/pub/epel/6/i386/epel-release-6-7.noarch.rpm

remi:

rpm -ivh http://rpms.famillecollet.com/enterprise/remi-release-6.rpm