Oh, funny, I was just thinking of asking this same question as I resurrect a Mac G4 from about 2001, running Mac OS 9 (not OS X). There's a whole website and forum[1] for that, though.
I read this list a lot more than I post. I enjoy some of the tales of old machines, especially anything DEC. Sometimes I learn things from tangentially off-topic posts (like discussions of software tools and image file formats best for making archival copies of documentation, or the best formulation for trapping fruit flies in the kitchen). Personally, I'm not very interested in C64, TRS-80, or peecees, but that's just me. It takes me a trivial amount of time to delete a message and move on to the next if I'm not interested. Since the average traffic is low, I don't have a problem with a low bar for "on topic". Perhaps a good but blurry line is "old enough not to be of much practical use anymore for most people, but significant in the history of computing for some reason"? [1] http://www.macos9lives.com, for anyone else playing with such toys.
