Using GIMP to produce "High Dynamic Range" digital photos

I produced this image after reading this article.  It describes a way of combining multiple separate digital photos together to get 'round the problem with digital cameras have (even the good ones).  Put simply they can't capture well, scences where there is a big range of lighting from dark to light.

The original shows how much less detail is reproduced in the bright clouds, and the dark foreground.

Infact the "original" was one of three 'bracketed exposures' - the camera takes the picture with its normal settings, then imediately takes one that will me slightly over-exposed (but capture more detail on the darker area), then one which will be under-exposed (but capturing more detail in the lighter areas)