The *current* Debian will run a-okay on a Pentium 200 with 96Mb of RAM. I know this because that's what my server is.

I wouldn't run X on it, though. Well, actually I wouldn't run GNOME on it. It would probably do quite okay with XFCE or WindowMaker. But for a lightweight website and mail server, it's fabulous. I've learnt a lot running that on an old server.

Wade.