Adding additional source of packages (software) for Centos will greatly reduce the need to recompile OSS packages. Epel provides open source software that is free for use. This includes clamav, atop, cacti,
Here are step to add a common repository.
Centos 5
Step 1: install and enable epel repo
rpm -Uvh http://download.fedoraproject.org/pub/epel/5/i386/epel-release-5-4.noarch.rpm
Centos 6
Step 1: install and enable epel repo
rpm -Uvh http://download.fedoraproject.org/pub/epel/6/i386/epel-release-6-5.noarch.rpm
Step 2: Enable priorities
yum install yum-priorities
Edit /etc/yum.repos.d/epel.repo
add under [epel]
priority=10
