If you can read chinese...
www.baidu.comIt has a whole mp3 section, with top 100 new songs, top 500, artists, etc.
It is basically popular music that young people listen to. I was in China over the summer and I heard some pretty good songs on the radio and on tv.
If you want to hear some more classical chinese music with a younger, newer blend, there are many concerts on tv, on the CCTV channels that randomly pop up once in a while. Also some shows on tv where people preform (not to mention chinese idol). Music stores on the street have the newest and hottest CDs. Just asking the employee which ones are hot would do the trick.