RE: 360 -> Computer through Zune
You just need Windows Media Player 11. It has it built right in.
Once you install it, run it. Select Library and in the drop down menu select 'More Options'.
Make sure your Xbox360 is turned on.
Select the Library tab. Click the Configure Sharing... Button. Put a check mark in 'Share my media to:' Select Xbox 360, and select Allow.
Once in the 360 select the Media blade. Pick Music, then select Computer. You now have your library of music available on Xbox360.
You can add/subtract music/pictures/movies via the Library in WMP-11