Recently I acquired a NSLU2 and have Debianised it, it is now serving inside the airing cupboard at home. I am using it has an SMTP gateway and DNS/DHCP server, I have configured it to forward all mail on to my main mail server (sandman) and dnsmasq is now serving DNS/DHCP rather than the bloated ISC BIND9 and DHCP3 setup I was running before.
My favourite bit is the name for my new server — beast!
I found some really useful pages on the web when I was doing this: