[ edited version of author's www site ]

This plugin losslessly decomposes a layer of an image into layers
of wavelet scales. This means that you can edit the image on different
detail scales (frequencies). The trivial recomposition of the image
can be done by GIMP's layer modes so you can see the results of
your modifications instantly. Among the applications are retouching,
noise reduction, and enhancing global contrast.

The plugin can be found under "Filters > Generic > Wavelet decompose"

WWW: http://registry.gimp.org/node/11742