GC Shadow V1.2 is an enhanced replacement for GIMP’s Drop Shadow procedure. It supports Color & Gradient Drop Shadow, Glow, Inner Shadow & Inner Glow. Compatible with GIMP 2.6.x & GIMP 2.8.x with support for Layer Groups.
For Script-Fu coders, this procedure allows the passing of the Shadow Layer Name as an argument.
Support thread located on Gimp Chat