Last.fm is a service that you can use to collect all the music you listen in order to generate a profile about your tastes, if you add a subscription of 3€/month you can also listening radio based on general recommended music, an artist and so on. I find also very useful to look for festival or concerts, in particular to discover new bands that you might like because close to your music tastes.
After some time I renewed the last.fm subscription for additional 3 months and I discover a set of nice reports on my music tastes:
Baloon race: summarize my listening in 2010 compared to 2009
Clock map: summarize what time I was listening music
Trend map: shows my listening trends over 2010
There are plenty, most of them are accessible also from the free subscribers, few of them are reserved only to paid accounts. To be tried 😉