GIMP Sprite Sheet Toolkit

Exports multiple animation frame layers into a single spritesheet.
Imports the spritesheet image, cutting it into multiple animation frame layers.
Switches back and forward between animation frame layers (hiding the others).
Based on SpriteSheet ( http://registry.gimp.org/node/20943 ) by brian.schultheiss.

Get it here: http://registry.gimp.org/node/25915