"Ashley T. Howes, Ph.D." lists@ashleyhowes.com
[...] By large, I mean more than 500 machines. Think of a large university lab or internet cafe, where people can login to any machine, do their 'work', access their files independent of terminal used, etc.
You may also be interested in http://www.hands.com/d-i/ as well as FAI.
UEA used NIS when I was there, which can do users, passwords, groups, hostnames, automounts and more but you probably want LDAP these days. Surely other platforms can speak it better than NIS.
NFS can serve quite a large audience if done carefully and monitored and it fits easily with unix-style security, but it's prone to network problems and small incompatibilities between clients and server. If you get it right, I don't think it's really been bettered yet, but take a look at what the current thin client systems use.
I don't know whether mounting tmpfs as /tmp would discourage people saving there. Ultimately, if you want a reasonably complete system, people can save in a temporary place.
SNMP, MRTG, Nagios and probably other tools could monitor the network. It depends what you want to do and what equipment you have, but you knew that already...