I just found out about this. It seems pretty handy if you use gimp and need a quick normal map based on shade.
Yeah, it's not a bad plugin, although I prefer my TexGen tool over it. Usually because I want to fabricate my own normal maps from nothingness
Some other plugins you may find interesting:
Texturizer (seamless texture generator). Maybe not a terribly useful authoring tool for games, but I'd like to learn the algorithm to do it on the fly for various runtime effects. It's pretty damn cool to take an arbitrary image and make it seamless. There was another plugin that could alter an image by culling out parts of the image or expanding on parts of it (like stretching a lake to make a panoramic) and it didn't alter the image quality much. It was really cool, but I don't remember what it was called.
Denoise. Works very well, but very complicated to use.
GMIC (various filters 'n stuff). Nice collection of artistic effects you might want to doodle with.
Thanks. I'm taking a look at them. Texturizer does seem cool. I'm going to play around with it a little bit.