What do to with older computers?

I have some older, slower PCs. There are a couple that still have DOS and Windows for Workgroups 3.11 on them that see little use now. One has OS/2 Warp version 3. Another, not just too slow I suppose, has Windows 2000. There are a few machines that aren't really on the network yet - or perhaps I should say not on the network at the moment. A couple have been retired from firewall/NAT service. A Pentium-90, and one or two Pentium-166s are sitting around. I'm wondering what to do with them.

One machine I had planned on using as a Linux distribution testbed. Install some distribution and see if I liked it, and if I did, put that distribution on belgian, my primary computer. Alas, 166 MHz seems to be too slow for almost all distributions nowadays. Or at least the ones I'd care to run as my primary operating system. I looked at upgrading things, but it's actually less expensive to get a new machine outright.

It seems wasteful to just scrap the old machines, though they're now so old nobody else really wants them either. I think even Computer Renaissance stopped taking in first generation Pentiums as trades. What could they do with them? But rather than figure the old machines as junk, I'm willing to at least look at them as toys. There must be something they can do that isn't already being done by the other machines. Perhaps I could play around with some of the truly alternative (pretty much toy) operating systems on them.

A while back there seemed to be a few of these little oddball OSs around. Now that I'm looking for them, they seem to have gone missing. I figure I'm just not looking in the right place(s).

Any suggestions for what to run on a 90 MHz or 166 MHz Pentium?