Written by Stefan Ott, this is a plugin to control your V4l radio device.
First, add the plugin to your panel.
Then, to switch your radio on/off, simply left-click on the plugin's icon (by default it says “- off -”, if it's turned on it displays the current frequency).
Once turned on, the middle button will show you the station preset menu. This is also the place to set the frequency you'd like to tune your radio to.
The mouse wheel allows you to change frequency or station preset. You can choose your preferred behaviour in the properties dialog (right-click menu).
You can find older releases of this plugin at http://archive.xfce.org/src/panel-plugins/xfce4-radio-plugin/
To run it, all you need is the Xfce panel and a properly configured V4l radio device.
To compile it yourself, you will need the corresponding Xfce headers as well as your kernel headers.
Bugs should be reported to the Xfce bug tracking system.