This one shows how I draw my recent "vintage" pics. It's not really a tutorial (as in step-by-step lesson), but it can still give you some hints on shading in general.
Just a warning: the subject is a sexy male demon, please don't look if "pretty" males make you feel uncomfortable :]
If it doesn't fit your screen (it's big, 900 pixels in height), try to download -- it should open in a new window and resize Flash to that window.