If you have to deal with a very large site - dozens to hundreds of hosts - you'll need more than what Phillip suggests here. Here are a couple of suggestions:1) Become a member of USENIX. The USENIX LISA (System Adminstration for Large System) conferences are an excellent resource, and if you're a USENIX member, you can can the papers on-line.
2) One resource that was talked up at LISA 98 was the cfengine tool. Go check http://www.iu.hioslo.no/cfengine/ for more details.
3) If you have lots of systems, having a model for going about doing it is more important than what tool you use. (Once you know what you're trying to get done, there are many tools that will let you accomplish your goal.) I was very keen on a paper at LISA 98 called "Bootstrapping an Infrastructure"; the authors have made their paper available at http://www.infrastructures.org.
-- Paul Holbrook, January 25, 1999