Adding alternate repositories to CentOS

Many alternative repositories are available to install software packages for CentOS. Popular alternatives and instructions for adding each are listed below.
EPEL – Fedora Repository
sudo rpm -Uvh http://dl.fedoraproject.org/pub/epel/6/i386/epel-release-6-7.noarch.rpm
Note: Get the latest version from here: http://fedoraproject.org/wiki/EPEL