Did a search on a couple forums and the web. None of the few techniques were simple and straightforward. All I want to do is make a circular crop. Creating the circle is the easy part but I still have white areas outside of it.
There is probably another way but this will work. BTW- You will need to save the image as TIFF or PSD.
Make the circle with the Elliptical Marquee tool, Image > Crop, then Invert the selection (CTRL Sft I), use the Background Eraser tool over selection to erase all pixels.