GIMPminimizer is a freeware tray application that minimizes all GIMP windows when main GIMP window is minimized. GIMPminimizer also restores all GIMP windows with main GIMP window. In addition, you can start GIMP by choosing "Start GIMP" menu option.
http://www.mystercrowley.com/files/GIMPminimizer_v1.0.zip
http://www.mystercrowley.com/files/GIMPminimizer_v1.0.zip