ghosting_addon.py (by Leiro) doesn’t work with recent builds of Blender, perhaps because of bmesh. I tested it in 2.62 and it worked fine.
Does anyone know Leiro or how to get hold of him? I’d like to find out if it’s possible to update the script.
Failing that, does anyone know of something similar? In case you aren’t familiar with it, it adds ghost outlines of preceding and subsequent frames, sort of like onion-skinning.