I wanted a Mac Mini for the longest time. friend up in Ontario acquired a bunch from the school district and locked them up inside his office. he did have fun trashing the eMacs being retired at the same time, however... so big that they didn't even fit in the largest garbage cans the school had-- so they went straight into the dumpster after being stripped of hard drives, RAM and DVD drives. I'm told they made satisfying, heavy crunches as they piled up. (don't worry, they were the horrible 700MHz ones.)
From what I understand, he still has them in his office, to this day, in a neat stack of about 10-15 of them or so. they're most likely the 1.25 model because schools are cheap, but I used to want one of them badly. ended up getting a late 2009 high-end Intel Mac Mini and upgraded that to max specs (which for the hard drive has a new max of 2TB now and I'm still on a 1TB drive for it...!) so I haven't really asked about them much.
there IS a market out there for the mac mini's, but they won't move in large numbers for at least another few years. G3 stuff is starting to get expensive now as supply dries up, and G4 towers are going for 200 a pop on fleabay.
it's also my understanding there's a Mac-oriented community of audio people with old music gear that has drivers only for MacOS 9, that's usable otherwise aside from that. I think there's some OSX stuff mixed in there too-- but I'm not sure if those require PCI slots to take advantage of or if that's USB/Firewire stuff that a Mac Mini could handle. most I have for Mac audio equipment is a 3rd revision (pre-white box) Griffin iMic.