I set up various music players around our house and my work to report back to Audioscrobbler a couple of months ago. Audioscrobbler keeps track (heh) of the music you play and summarises it all. Kinda cute.
Our (me and Louisa) profile is at: http://www.last.fm/user/johnandlouisa/
We listen to music together, but also separately (me at work too) so the results can often be skewed towards each others tastes, but we share a lot of musical interests. See if you can guess who is listening to what in particular.