Our vet used to have a list of everyday foods that were potentially poisonous to dogs - I remember chocolate, grapes / sultanas / raisins, macadamia nuts.
I suppose some dogs will react worse than others and it will depend in part how much the dog consumes in relation to its size.
Still, it would be plain daft to either give your dog these things or leave them where the dog can access them. I know accidents can happen, though.
Just really glad that poo - horse, sheep, hen (but not cattle - wrong consistency, I think) - is not poisonous or we'd be in real trouble here