Remote, Automated Configuration of Unix Boxen?

drift factor asks: "I work for a small company with about 200 Linux desktops, all identical aside from hostname and IP information running Redhat from a kickstart install. Currently, when something needs to be changed on all of them (say, the default gateway) we either have to ssh into all of them and do it manually, or write a Perl script to do so for us. Is there a good remote configuration system that will also allow some level of automation, i.e., I tell it what IP I want the default gateway to be on each machine and it updates them for me?" If you manage a large server farm and have used or written utilities that do this, please share your experiences.