Black Knight Chess
This app has different difficulty levels and you can choose to play against the computer or another human. Fun!
I like this app because it shows you all of the possible moves a piece can make when you tap it and it also keeps track of all of the previous moves. Very Educational.
Next best thing to an Instructor. If poses could be added to workouts it would be 5 Stars. Great motivation and ease of use through guided workouts. There are others with more poses but no guided workouts.