Here’s a quick little tip on how to add drop shadows to via the command-line tool ImageMagick.
The command I used for this image was:
$ convert <input file> \( +clone -background black -shadow 50x8+0+5 \) +swap -background none -layers merge +repage <output file>
50x8+0+5 controls the appearance of the shadow. The first value controls the opacity, the second one controls the radius and the two last ones controls the left/right and up/down alignment of the shadow.