Not sure what you are aiming to do, but you can find all non-CentOS packages by the command on this wiki:
http://wiki.centos.org/TipsAndTricks/YumAndRPM#head-0424f619b79e293fc743a397...
Akemi
Thats exactly what I need, is there a simple way to pipe the output into rpm or yum and remove all that? Thanks! jlc