Here is a list of WordPress Plugins that are built for online radio website.
Native Flash Radio WP Plugin
Worldwide first browser based standalone HTML5 MP3 Radio FM Stream Plugin.
Radio Utilities
Radio Utilities is a great tool for your WordPress website.
Radio Player Shoutcast & Icecast WordPress Plugin
Background Music Player
This WordPress plugin allows you to play tracks and radio streams right on your WordPress website.
WordPress Artist / Band Manager
WP Artist is an all in one Music solution for WordPress.
StreamyPlayer WordPress plugin for Video Streaming
Streamy Player for WordPress is a very lightweight player for the WordPress platform.