I'm not sure how useful it is for most people, but I came up with a method for synchronizing music playback for multiple xboxes. I can see this being useful if you have a sound system setup in multiple rooms or different floors.
If there is some real interest, i could probably be talked into creating a program for this.
Directions here:
http://www.gamerhistory.com/forum/viewtopic.php?t=656