We have lots of music resource on the internet, internet radio is one of them. ShoutCast is a very good online radio directory that collects over 45,000 different kind of radio stations from around the world. It doesn't have fancy interface but very clean, and easy to play. Just browse "Radio Genres" or "Featured", pick anyone you like, it will play program with a simple media player in same page or popup a small window. It also offers embed code, you can paste it on your personal site.
For audio material holders, ShoutCast allows you to create own radio station. Yes, you have to register an account, download a client, follow instruction to set up. The stream music service powered by Winamp. This website also belong to AOL.