Netbsd/mac68k 1.4 or 1.5 could be fun as a quake server, or smtp.
Openbsd 2.9 great for security if you want a remote ipsec tunnel,website, or apache ftp.
Linux/m68k dowsnt have to much support I’d back peddle to mklinux to use as a print server or install mac OS 7-8 and install macten.
It all depends on what you will use your 68k mac for. Believe me its better to take a function away from your everyday machines and give your old machine a single purpose. For example : I have a pm7100/66 video phone, pm6100AV hooked up to my DVD and vcr for quick editing, 8100/80 +umax powerlook scan and ftp server w/macten for telnet. P2/400 NT exchange server, P3/800 win2k/winxp , 7100/66 mklinux for anon email sending, print server and chat, etc.. you get the idea.