Shane Prigmore's character development is the ones I find most interesting. I love the first image as it shows how much her character has developed in style, yet you can still familiarise that that is Coraline. The second image is later development sketches, still by Prigmore, showing her different facial expressions within the same framing of the hair and face structure which doesn't change.
Other sketches he did was ones of Coraline's parental figures. The first of these examples being her real father, and the second her 'other mother' from the other world. I love how just from comparing these two characters you can see the dullness and boring expressions on the fathers face, matched with the tones used to depict him, contrasting with the vibrant colours and postures used to show the over-the-top personality of the other mother.
My favourite image of all though has to be this one, showing the drastic differences between the usual mother and the 'other mother'. Even with the image on the left having a coloured background, the expressions on her face showing tiredness and unhappiness brings the feel of that character down to a negative. Whereas the well kept hair, rosiness of cheeks and wide smile of the twisted and slightly (in-fact very) scary other mother, makes us perceive her to be the better of the pair, which is very important in the telling of the story.
Prigmore's blog is: http://shaneprigmore.blogspot.co.uk/
Another useful blog if you are interested in the concept art of Coraline is: http://nicocartoons.blogspot.co.uk/2009/03/coraline-concept-art.html