This was pretty nifty, and it worked on the first try on my home network where each computer has a static IP. Presumably, you already know about VLC -- a very cooperative media player that is available on Linux, Windoz and Mac.

I started by logging into one of my linux boxes over ssh and ran the following command:

vlc video.avi -I dummy --sout udp://XX.XX.XX.XX:8080 --loop

note you need to replace "XX.XX.XX.XX" with the IP address of the machine you want to receive the video

To play the video on the other machine, simply run:

vlc udp://@:8080

I still have yet to try this over the internet. I wonder if my humble DSL connection can upload fast enough to support the stream.

Lots more goodies like this over on linuxtv.org