Amua is a status bar application for Mac OS X that allows you to control Last.fm web-radio streams. It is an alternative to the official Last.fm player.
AudioRack is an open-source radio broadcast automation and live assist system. It features: arserver - a faceless (daemon) eight bus audio server, AudioRack - User interface, and a database server.
BBC Radio Widget
BBC Radio Widget lets you listen to all 60 of the BBC?s national, regional and local radio streams, right on your Dashboard.
FStream is software for web radio listeners. It decodes OGG Vorbis, AAC/AAC+, and MP3.
iScrobbler lets you submit your music listening habits to AudioScrobbler.com.
(commercial) Nicecast broadcasts music from OS X. Broadcast to the world, or just across your house. Nicecast can help you create your own internet radio station or allow you to listen to your iTunes Music Library from anywhere in the world!
Raclette is a nice add-on if you like to listen to [CT - Das Radio].
RhapsodyX is a small application that resides in the menu bar and scrubs your listened-to tracks on rhapsody.com and submits them to last.FM.
StreamRipperX for OS X lets you save Internet radio streams, song by song as MP3 files.