Funnily enough I was also working on something along these lines.
I was taking the approach of listing each plugin by its menu name (categorised by the main Paint.net Effects types). I was also running each plugin on a sample image (or blank image for render plugins).
Effects are such visual things I thought it was worth seeing what they are like.
e.g Parrot is orginal image, then apply each effect to it. So far I've done about 100 images.
I was thinking that it would help to have both the DLL filename (some effects are in combined dlls) and the menu name as well as a link to the relevant Plugin forum topic.
My ultimate intention was to have some web pages that would show the images and you could click on the link to see the thread about that plugin. (view the attached image to see what I mean)