In this world of "There's an App for that", I thought I might put in my 2 cents about the ones I found fun/useful. Please remember that these apps in no way replace your veterinarians office. We are always happy to talk on the phone and examine the pet if need be.
PetSnap: Pet Photo App. It has several sounds(squeaky toy, cat meow, bells, etc) to help get your pets attention to get a great picture.
Pet Phone: Allows you to put your pets health needs on your phone. It tracks vet visits, medications, weight history and general info about numerous pets.
PetBook: Its a calendar but it also have notifications. It can remind you to medicate your dog or that it has a grooming appointment.
ASPCA Petoxins: It has a list of toxic plants, with pictures and the symptoms they cause. You can also call Poison Control from the App and get advice(I think there is a fee for this).
Dog Tricks - Best of 101 Dog Tricks: This teaches 8 basic tricks. Would be good for new dog owners.
Dog-a-Log: Its a list of dog breeds with pictures and descriptions. It is collected off of Wikipedia, and put in to simple app form.
Pet First Aid by Jive Media: It has information on what do do in an emergency situation. (Burns, bleeding, choking, etc.) It also has fundamentals for restraint and muzzling, with very helpful videos. I think this is a great app for all pet owners to have.