Ok. I'm almost finished with setting up just that on a arm-based Hercules eCafe EX HD. Though the eCafe uses Ubuntu while the Pi should mainly un Debian, most stuff should be very similar. The eCafe works very satisfactorily, using about 10% of CPU (Cortex A8@800MHz) and 50k of RAM at full load. So...
The server is designed to run screenless/keyboardless after setup. It'll boot to a console, and auto-run all required software. Files are assumed to be on an external, mechanical HD.
List of stuff to do and install
OS: Debian, console mode. We'll Probably keep X11 around because it'll be on the SD images, it's impossible to remove it without breaking apt-get, and even on a 2GB SD we'll have spare space.
- samba, to share drives with Windows PC both ways
- ssh, to remote connect to a console from Windows
- transmission-daemon, for torrents, controlled via the web or the console.
- miniDLNA, a non-transcoding, very light DLNA server.
- htop, fun list of stuff that's running
- links2, because the web is so much better in text mode
- mingetty, for autologin (not sure)
- pastebinit, for when you need help
- backup script, for the data drive and the system SD
- a build environment to compile miniDLNA, though I'm sure binaries will be available shortly after the Pi is released, if not before
- X11, expecially if you have no other Linux PC, for gparted. Also, gives access to a "true" browser. Text-based links2 is funny, but not very practical
Those 2 are convoluted to install, so we'll not cover them here.