I had success using with Canola and the new Google Media Server gadget for Google Desktop, which acts as a UPnP server for all of the media files it crawls on your computer.
http://desktop.google.com/plugins/i/...ver.html?hl=en

I'm not sure if it will meet all of your criteria, but since it is new I thought I'd mention it here.

Well VLC will be ported to NIT (see here)
So basicaly you could use it as a streaming server on your home network and you could use the client interface from your N800.
The smartest way would be to use the http interface through the plugin for the web browser.
There is some projects for a php VOD interface using the VLC plugin (see here if you speak french).
I successfully used this solution for years to stream movies from my private network on my professional laptop when I'm abroad, so I hope we could do the same on NIT.
There is some very alpha builds of VLC for maemo on this thread.

I've heard good things about VLC, but to be truly usable on a "low-rpm" ARM engine it would probably need a lot of optimizations (both perf + power mgmt) which may not be within the scope of a SoC project.

Wrt streaming media to Nx0, have people tried forwarding video from p2p clients like TVants or Sopcast to the tablet? The original resolution is sometimes too large for the tablet's screen and also bandwidth-wise, but if the feed could be buffered and transcoded on the fly when needed..

IIRC Sopcast does have a native (?) Linux client, but on a home network the PC could handle the upstreaming and a pass the feed via WIFI to the tablet's media player.