This is my first attempt of creating a plugin for the FCKEditor. This plugin utilizes JW_Media_Player found at http://www.jeroenwijering.com/?item=JW_Media_Player at will play FLV files as well as MP3.
To install, just unzip the files into the plugins folder. Configure the editor to see the plugin (FCKConfig.Plugins.Add( 'flvPlayer','en') ;). And add the toolbar button to your preferred menu.
Like I said, this is my first attempt, so please be gentle.