During the summer, I put together a simple server / client combo based on Avahi / ZeroConf services, but it didn't get to the point I was looking for. I have this next week off and will try to work on it again.

Use cases:

• Dan has several computers for his family. He wants to have a central server for common things like music, movies, and photos, but he doesn't want to spend a bunch of time configuring the server and clients only to teach his family how to use the services. Everything should just work and be mind-blowingly simple.
• Gail wants to use her PS3 or XBox 360 to play videos on the TV and have the same videos available on other computers in the house.
• John wants an easy backup solution and caches of updates to keep his bandwidth down.
• Julio wants to use his smart phone or computer to control a central jukebox for the apartment.

Features:

• File sharing broadcasted by ZeroConf so that no configuration is necessary on the client.
• Music is published so that DAAP-aware players like Rhythmbox and iTunes can have immediate and automatic access to it with no configuration.
• Music can be played on the server using MPD, controlled by either clients or the server with as little configuration as possible.
  
• Videos are published so that uPnP-aware hardware players like the PS3, XBox 360, and Netgear models and software players like Elisa, XMBC, and can play the content with no configuration.
• Videos can be played from the server and controlled by either clients or the server with as little configuration as possible. This may require VLC and a web interface. I need to look into it.
• There needs to be a backup solution which get as little configuration as possible.
• There needs to be a package-sharing solution. Should this be a cache or ZeroConf?