Apps similar to RadioEnhancer include Pithos, which is free and open source. Other options are Pandorita and PandoraBrowse. In total there are three Internet Radio Services like RadioEnhancer for Mac, Windows and Linux.
Pithos is a Pandora client for the GNOME Desktop. The official Flash-based client is a CPU hog, and Pianobar is command-line only. Neither integrate with the desktop very well, missing things like media key support and song notifications.
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Pandorita is a native Mac OS X client for the internet radio service Pandora. It is written entirely in Cocoa, and built to be lightweight, easy to use, and fully functional. Internally it uses the amazing pianobar library to communicate with Pandora's server.
PandoraBrowse is a mini-browser for Pandora that allows you to minimize the music service to the task bar.
