The Z stands for "Zephyr", the MIT Athena Zephyr Notification System. Zephyr started out in 1986 as a messagin system for operations staff to send out messages like "your home directory is going off line" or "scheduled outage in 10 minutes" or "your print job is done." It rapidly evolved into a person-to-person and person-to-group messaging system among the MIT extended community.
There are a number of long lived "groups" (called "classes") that have arisen over the years, usually associated with social or technical groups within MIT. One major theme has been that obscure technical discussions show up everywhere, simply by the nature of the participants. In order to channel these discussions into a place that they'll be most appreciated, class "geek" was created.
On class geek, discussions are fairly wide ranging, but typically high in technical detail. Some participants have asked that the more informative threads be preserved for later reference and study. Since the existing automatic recording systems do not cover class geek at this time, I've gathered some of the specifically requested threads here, with minor reformatting and permission of the participants.