My best immediate guess would be to create a blank transparent canvas. Then make a new layer and using the rectangle shape tools make a rectangle the size you want it. Then lower the opacity of that layer to 0. Then right click, click blending options, check/click Drop Shadow. - Jordan
Hello there, the effect can be done in 30 seconds! Create a big BLACK (preferably black, you don't want the shade to be brown or yellow ) rectangle (make sure the height is more than the width), make the gaussian blur to 3px, then scale it in west-east and use a marquee tool to draw a rectangular selection lil' bit smaller than the previous rectangle. Erase.
Draw a rectangle the size you want, fill it with some random color, and mess around with the drop shadow on it until you get it right. Rasterize the layer. Take the Magic Wand tool and select the random color, press delete.
Hi! I found an useful PSD file at Graphicsfuel, hope you like it: http://www.graphicsfuel.com/2011/04/content-box-shadows-psd/ Regards!