[CentOS] mirrorlist(for nagios or snort)

Mon Apr 30 16:00:41 UTC 2007
Pitshou Asingalembi Mbema <depitsho at yahoo.fr>

hi,
i want to know how i can find a mirror for installing nagios in centos 
4. Because when i do yum search nagios or yum install nagios i don't 
receive a response.I don't know if somebody can give me a website like 
apt-get.org(unofficial apt repositories).
thanks