Here's a link to walking dandruff - it's called that because the mites are carrying the flakes so you can see them move.
http://www.petplace.com/dogs/cheylet...ite/page1.aspx
If they're not moving then I would think it is probably seborrhea - Virbac makes a shampoo called Sebolux that you can get from your vet. I know they do make human shampoos sold over the counter for this condition, but I've never tried them. You need to leave on the shampoo for 15 minutes for it to be effective.