Debian Stable (Sarge) latest netinstall, the "joe" (jstar) editor, Samba, and a utility called SWAT to configure Samba from a web browser. Designed to be minimalistic (takes up very little resources), work "out of the box" for all clients (Win2000,XP), share everything read-only, and be easy to admin.
You can always install more software in the VM if you want, it's Debian. The initial HD is deliberately kept small to make downloading easier; additional disk(s) can be added later if needed.
Based on what beta-tester feedback I get, might include a few more utilities in the base install, different kernel, drop a SCSI card in favor of Ethernet, etc. But personally I'm inclined to keep it as small and focussed as possible. However, I also plan to put most of the same scripts (updated, of course) that went into my Squid appliance in before general distribution; but this is just the initial release.
I've used its win2k-based predecessor to install Norton utils, autopatcher, Invirtus stuff, etc on Win guests. Would like to know how it performs under a server environment with multiple clients putting load on it. (The iso's are all stored on the host, so I kinda have big hopes for it. 