This article shows how to Fade out Images and make them washed out in GIMP. The washout effect is created by making colors lighter.

Jack Wallen shows you how to easily "key out" a green screen from a still image in The GIMP.

I needed to remove the white background from several hundred images in PNG format and replace it with transparency. I know you can automate Photoshop but that’s like getting into a Sherman tank ...

In the Gimp, you should be able to simply use the elliptical selection tool (E) to select the area you want, and then either copy and paste into another image, or Select->Invert (Ctrl+I) and then ...