Hmm, sometime I should run out to St. Vinnies or Goodwill and pick up some of those old boxes, fix them up and get them online. I have plenty of space for machines (huge walk in closet)
Believe it or not, you don't need a lot of power to run a server. Even a spare 233mhz P2 we could put to use in some way. The programs that we currently run aren't very CPU intensive. (The only exceptions are the fast machines, where we could run web or ftp servers, with permission of the machine owner of course).
Also, let us know what connection type you're on if you want to run a server with us (e.g. max bandwidth, monthly bandwidth limit if any, restrictions on what the ISP allows you to do, and network topology from the box to the internet (routers, switches, NAT boxes, firewalls, etc))
Also, machines you want us to use should be connected to a wired LAN, not thru wireless as wireless can be too unstable. Again, a box that is being used as a workstation doesn't count as a proper server, or boxes that are going to be toyed with in other ways. Or boxes where the power cord might get pulled out.
Again we take preference to people running Linux boxes who would be willing to give us full root access to the box.
If you want to run a server but don't have the technical knowledge to install a proper OS, let us know and we can walk you through installing the OS.