Are you looking to get "therapy pet" certification or to do visits to nursing homes, etc? I was certified through the Delta Society, but only medical professionals, psychologists, social workers etc. can be certified in pet therapy. It's more involved and you work directly with patient one on one with other health care professionals. They also have the Pet Partners program which is fabulous! You have to check their website for contacts/classes in your area or you can take the course at home via video and take the written test at home as well, but both you and your pup must go in person for the "clincial" testing Here's the link

Delta Society

You can also go the CGC route. A lot of nursing homes and realted facilities will accept a dog that has been CGC certified. Good luck!