[CentOS] Post postinstall configuration

I'm building kickstart files for use in doing automated installs of
various systems.  I would prefer to do fairly minimal amounts of work
in the "%post" and postpone further installation and configuration
until after the first reboot (or even later).  It should be easy
enough to add something to rc.local that will download scripts and run
them, but I'm wondering if there is a preferred technique.  I haven't
found anything in the Red Hat documentation I've read so far.

This isn't about figuring out a way to do the update, it's about
trying to follow the "Law Of Least Astonishment".  I've dealt with too
many really screwed up systems that had customised stuff everywhere
and nothing worked as expected.

Suggestions?

-- Matt