I made these plugins for myself and a few of my friends who wanted a very simple method of doing chroma key compositing. I was working toward a stand-alone program, but when I ran across Paint.NET I was able to get things running very quickly. I tried using tarheit's plugin, and while it works well, it is more complicated than what I wanted.
The plugins work pretty well, although I didn't do a lot to try to speed them up. SimpleGreenScreen has a single slider (I wanted it to be easy enough for a six-year-old to use), and works with green or blue backgrounds. SimpleChromaKey works with any color background (it requires the key color to be selected as background before running), and has three sliders: two for color tolerance, and one for shadow correction.
I am posting the plugin DLLs, and a flat text file with some documentation.
mgeorgiady
SimpleChromaKey.zip