I work at the university. In my institute we have six computer laboratories used for teaching. Each lab has almost 20 computers, which gives over 100 machines total. Computers have either Windows XP or Windows 7 Eneterprise operating system. We use Symantec Ghost to manage all the computers. Each computer has a Ghost client installed, which allows to control computers over network. Every six months we restore a master image on one of the computers in a lab, update that image and distribute it over the network to all computers in a laboratory. Thanks to Ghost client this is done automatically with just a few clicks.
Recently I suggested that it would be good to have Linux installed in the laboratories. The administrators were concerned that we would not be able to manage that many computers if each would have to be updated manually. The question is: how to manage such a huge network of Linux machines in an automated way?
To make the description of our network more complete I'll add that all students have their accounts (about few thousand users) on a central server. These are accessed via LDAP. To use a computer in laboratory each student has to log in using his own account.
Best Answer
As previous answers say, you have very powerful tools like Puppet, chef, cfengine for advanced configuration management.
But if you want a tool that can do installations, easily manage configurations, deploy systems from templates, apply updates, or remotely execute custom scripts... you can try an integrated solution like SpaceWalk, which is the open-sourced version of the RedHat Satellite. Note that it can work with other distributions, not only Redhat!
I've personally used the commercial version to manage more than 1000 hosts.