My vintage computer collection as of June 2016
I couldn't help but notice that you don't have Linux on any of these machines. I really like Damn Small Linux as a Windows 98/ME replacement, with it's 2.4 kernel it's far from a modern Linux Distro, but it runs extremely well on machines with very little (32MB or less) RAM. Of course then you can't run your vintage software, but it does come with a useful suite of software. Obviously there are heavier options that would be more modern, but I never had much luck with them on the kind of machines you posted about.
Do you have any working K6 machines? The K6 was always my favorite "vintage" processor, probably in part because all the Super Socket 7 boards I'd find had AGP slots for decent GPUs where as most of the Socket 370 boards didn't have AGP, admittedly they were mostly budget machines, so I'd have to stick with crappy on board graphics or a slow PCI card.