[CentOS] Installing a package group after the initial install

I recently installed a system using the CentOS 4.3 CDs which is now  
up and running.  Everything is running fine, but I forgot to install  
one of the "package groups" that Anaconda offers as an option.  Is  
there a way to install this group on a running system using the data  
on the CDs (i.e., not via a repository)?  If not, is there a way to  
get the list of RPMs that belong to a package group?  If I had that  
information, I could install the RPMs manually.

Thanks,
Alfred