1.) Open up a new file. About 400x400px. Set a background color, anything but black or white.

I used #FFCC00. Fill the background layer.

2.) Make a rectangular marquee selection.

Create a new layer, name it " white" and fill it with white.

De-select (Ctrl-D)

3.) Click on the single row marquee. Make a selection. Preferably near the upper part of the white layer. Then expand the selection by 4.

Create a new layer, name it "gray" and fill it with R: 219 G: 219 B: 219

4.) De-select (Ctrl-D) and Filter>Blur>Gaussian blur it by 2.

5.) Create a new layer, name it "gray 2" and make another single row marquee selection. This time, make the selection near the lower part of the "white" layer.

Fill the selection with black.

6.) De-select (Ctrl-D) then hit Ctrl-F to Gaussian blur it with the settings used in the previous layer.

And you should have something like mine on the left.

7.) Make another single row marquee selection above the white layer. Expand it by 2.

Create another layer, name it "gradient" then apply a linear gradient (foreground to background) going from top to bottom.
Use White for the foreground color and R: 168 G: 168 B: 168 for the background Color.

De-select. (Ctrl-D)

8.) Finally, make another layer and send it to the back of the stack of layers, name it "shadow".

Select the transparency of the "white" layer (ctrl-click). Now, fill it with black.
De-select and gaussian blur it by 5.

That's all there's to it in making some really nifty borders.

There are a lot of things you can add to these borders to make it look better (ie. inset lines, buttons, scanlines...)