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 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.