If you are looking for a way to stream media to either your xbox360 or your ps3 from a linux machine, then I highly recommend that you have a look at this project. Ps3 Media Server is a java app that you can use to stream all kinds of content to either device.
I have been using it for almost a year now on Ubuntu and it has proven to be extremely stable.
It also offers ‘on the fly’ transcoding which will allow you to play audio and video formats that might not be natively supported.
Here is the most well documented configuration guide I have come across while looking for tips and tricks.