What is CentOS?
CentOS is an Enterprise Linux distribution based on the freely available sources from Red Hat Enterprise Linux. Each CentOS version is supported for 7 years (by means of security updates). A new CentOS version is released every 2 years and each CentOS version is periodically updated (roughly every 6 months) to support newer hardware. This results in a secure, low-maintenance, reliable, predictable and reproducible Linux environment.

Overview
The CentOS-6.0 LiveCD is meant to be a Linux environment suited to be
run directly from either CD media or USB storage devices. It does not
need any persistent storage on a machine, which also makes it a suitable
recovery environment.
Due to space constraints, it was not possible to include all the
traditional desktop applications on the LiveCD. You can though enjoy a
Gnome basic desktop, view and modify pictures with gthumb and the Gimp,
browsing the web with Firefox, send emails with Thunderbird and connect
to your favorite Instant Messaging network with Pidgin
 
http://wiki.centos.org/Manuals/ReleaseNotes/CentOSLiveCD6.0 
http://www.centos.org/ 
http://ftp.ciril.fr/pub/linux/centos/6.0/isos/ (checksums)