Hi Gar,

I don't actually think the GIMP will be much help here. You could use it to do some processing on the HDR after you'd assembled it but I haven't yet come across a way of using the GIMP to do the actual HDR compilation. There's lots of options though, PhotoMatrix is popular, but I use Bracketeer because it's cheap! I then process the composed HDR in iPhoto. I do the vast majority of my image processing in iPhoto actually. This is the technique I use: http://www.bartbusschots.ie/blog/?p=744

Bart.