Very short article on Wired, so I found a much longer interview at shocktillyoudrop.com:
"Some of the costumes are constructed from scratch. There's one woman who was brought onboard who specializes in miniature knitting, making sweaters as small as an inch big. Equally impressive, though, are the costumes made from everyday objects. One of the models - a background townsperson - sits on the desk with an outfit made from an ordinary tube sock, recognizable only when it's pointed out as anything other than a sweater."
Also, RottenTomatoes has some 'behind the scenes' footage on crafting the film. Something interesting I had read a while back was that there were visible seams on the faces of the characters, those sections can be swapped out for facial animation. The director, Henry Selick, supposedly was in favor of leaving the seaming visible, but it was eventually decided to remove the seams digitally.
You can see the seams on the Mom at the 1:42 mark on the 'Crafting the World of Coraline' video at RottenTomatoes, I would love to see some longer scenes before/after the seam removal, perhaps they will show it on the DVD when released.