I thought this was a great article on, well, DOG POOP. We get questions here quite a bit on poo issues, and this may help answer some questions. The article contains pictures that are, albeit a tad gross, helpful.
Usually I paste the whole article into the thread but since this is a picture-dependent article, it is probably best read on the original site itself.
It is here:
Assessing Your Dog's Poop for Signs of Health Problem