This page is served up by my Mac LC 475, which lives just under my desk:
My LC has a 25MHz 68040 CPU (upgraded from the original fpu-less 68k), a mere 40MB of RAM and a 1GB hard disk. Thanks to NetBSD, an impressively efficient and frugal UNIX OS, this 1994 vintage Mac is still useful in production.
I decided it would be pretty cool to get a 1994 Mac serving 'Web 2.0' content, so I tried setting up a wiki. MediaWiki proved too slow, even using PostgreSQL and Wikipgdia. PhpWiki worked well, as did MoinMoin combined with Apache 1.3 and mod_python. Ultimately it was a little too slow to do anything useful with and I found that I didn't actually have a use for a wiki anyway.
I still liked the idea of using a 10+ year old server in production. Instead of a wiki, I thought that my LC might be more useful as a DNS server, so it's now a name server. DNS is such a lightweight protocol, so it handles a fair bit of DNS traffic without breaking sweat.
In order to get good performance from BIND, I removed Apache because of the amount of RAM it was taking up. Then I found out that my little server was linked to from the Old Apple Web Server Directory. So, to replace Apache I tried Lighttpd and it's brilliant, hardly uses any memory at all - about 480kB.
Update: As of late 2009, this LC has been running continously for 767 days. It presently serves as an IPv6 test bed and is presently accessible through an IPv6 tunnel provided by Hurricane Electric. I'm fairly sure that it is presently the only 68k Macintosh based IPv6 web server.