So, I have here a USB Zip drive (bought for an iMac).  Naturally, my first
thought was "hey, could I use it on my NetBSD box?"

Unfortunately, it appears not; it probes as ugen0, and I don't see any
trace of disk support in the USB code.

Is there anything like a published standard for USB disks, or is this
yet another case of the PC industry carefully standardizing too little
to be of any use?  (And is anyone working on this?)