Do dogs carry skin diseases, like ringworm, that can be transmitted to humans through touching?

Yes: Pets are a common source of infection with skin fungal infections (ringworm).

Diseases from dogs: Diseases that can be transmitted from dogs to humans are rabies, ring worm, leptospira, brucellosis, campylobacteriosis, tapeworm, giardiasis, hookworm, leishmaniasis, q fever, rocky mountain spotted fever, roundworm, salmonellosis, lyme disease, cryptosporidiosis, toxocara infection, flea tapeworm.