Two nice sites in one day, woo!
The body language site explores classical signs of dietary and mineral deficiencies. It's basic and easy to understand, and it's been put together by a team of researchers. Very nice.
And Ruby has a page on fingernail diagnostics: what ridges mean, why some people have white spots, flat spoon nails, and so on. Very nice, too. I tried to find the original site of the data, but couldn't. Shrug.