Get dominant colors from image discarding the background

Question

What is the best (result, not performance) algorithm to fetch dominant colors from an image. The algorithm should discard the background of the image.

I know I can build

Answer 1

Isolating the foreground from the background is beyond the scope of this particular answer, but...

I've found that applying a pixelation filter to an image will draw out a really good set of 'average' colours.

Before

http://img12.imageshack.us/img12/825/pixelate1a.jpg

After

http://img12.imageshack.us/img12/8127/pixelate2.jpg

I sometimes use this approach to derive a pallete of colours with a particular mood. I first find a photograph with the general tones I'm after, pixelate and then sample from the resulting image.

(Thanks to this page for the images found via Google Image Search)