[CentOS] replicate package installation on multiple machines

Hi all,
Is there a way to dump the current packages installed on a machine and  
use it do install/uninstall packages on other machines? I've  
configured one at install time but to speed up other installations I  
would like to install default packages and then install/uninstall some  
starting from my first machine configuration...

thanks

d

PS
Oh, I'm going to RTFM too... but I'm new to CentOS and yum...