Though the machine I have in mind isn't exactly "vintage" (it's from around the mid-90's), I plan on installing a distro of Linux with Apache, MySQL and PHP on an unused beige G3 tower. It is to be come my off-line web development test-bed. Since my wife and I are moving to a place without broadband (SHOCK! HORROR!!), we can't easily fiddle with code, upload, test, wash, rinse, repeat on a remote server. It'll also teach me how to properly set up Apache to work with multiple domains, something I haven't managed to grasp yet.
That sounds cool. I recently got a beige PowerMac G3 tower from a local university surplus sale. Needs a HD, but once I have one it will be neat to mess with. I also got a slot-loading iMac (400mhz) with a DVD-ROM drive that I installed Ubuntu on. So far I've been using it as a general-purpose internet terminal and I'm working on a game of Freeciv on there. Cool stuff!
By the way, I can help you with the multiple domains on Apache thing. I've had to do all kinds of text-line goodness to set up the VC&G server. And I'm about to do it all over again when I move it to a new machine.

RedWolf