A very useful plugin is that provided by RealNetworks -  RealPlayer is one of the best real-time audio and video delivery system for the Internet. By using this Plugin, you can listen and view thousands of hours of live and pre-recorded clips, including sporting events, live radio stations, news, music, and RealFlash animation. 

If you want to download 'freeware' versions visit RealNetworks' website at http://www.real.com/