I just opened Pandora, clicked on the 'mini-browser,' and then copied that address into Fluid.app. After creating the program, simply click on the Fluid menu choose Convert to MenuExtra SSB. You can even go to Preferences in your program (prior to converting) and select window styles and transparency.
So I now have a small menu extra with a pop-up semi-transparent window that I can instantly open and play/pause Pandora without keeping a separate browser-window open. Of course, Fluid can be used to make apps out of any other webpage as well. I hope others enjoy this as much as I am.

