AirFM is an online radio application written in Adobe AIR. Thus, it can be run on Windows and Mac OS X. The application is very simple and it comes with a few radio stations already added, but you can add your own if you want to. The quality of the ones included isn't something to write home about, and some of them even fail to connect.
The application is divided into three different windows: Radio stations, Radio player and Favorites. The first window shows all the included radio stations divided into country or genre. The available categories are: By Popular Demand, Russia, Ukraine, Rock, Anime, Classic, Electro, Latino, Retro, Universities, Jazz and Misc. In total, I estimate there are over 150 stations. Of the 10 that I tried, only 2 connected well. The quality of the ones that I was able to connect to was good enough. They sounded with MP3 quality, at least.
Adding your own stations is easy. All you have to do is add the URL of the station or of a M3U file.
All in all, this radio app works well. If you take effort of adding your favorite stations, you shouldn't have any problems with it.