I'm sure there are better people to answer this question, but cat-v.org is the personal blog & collection of interesting stuff by former plan9 personality uriel (sadly no longer with us). It hosts random thoughts and lots of interesting stuff (including man pages) about plan9 and early unix systems, and miscellaneous other unix trivia.

It really is a treasure. Take the time to browse, it's well worth it if you're somewhat interested in unix history and not overly familiar with the subject already.