Update April 24 2014: please note that the information here is now somewhat out of date, partially incorrect, and partially incomplete.
We have some mailing lists for local sysadmins. In the absence of a better resource page, I'm going to list them here:
ut-admins-request at the domain
Mailing list: hopefully the address is obvious.
that the actual mailing list is called
I say 'theoretically' because, as usual, topics can drift somewhat from the nominal topics, and I don't think either primary list has a strict topic.
At the moment, you don't need to be subscribed to either ut-admins or nw-admins to post to them, although this may change in the future. I don't know about the others.
As far as I know, none have publicly accessible archives. (The listserv lists may keep subscriber-only archives you can ask for messages from.)
From my somewhat slanted perspective:
General technical issues can wind up being discussed on either or both of ut-admins and nw-admins, often crossposted to some degree. Network issues and so on are generally announced to both; to some degree, I think high-level discussions tend to happen more on ut-admins than nw-admins, and as a result ut-admins probably has somewhat more rambling conversations than nw-admins. ut-admins is usually quiet except for periodic eruptions; nw-admins gets more regular traffic.
(If a constant drip of people asking about Windows administrations issues is going to irritate you, you don't want to pipe nw-admins into your primary inbox.)
Since Linux is by now probably the majority Unix on campus, ut-admins is the de facto campus Linux sysadmins mailing list; so far the traffic volume has not been high enough to split that off into a more specialized list. Thus, discussion of things like the merits of various Linux distributions does break out on ut-admins from time to time.