Harriet Hargrave's books are great for learning applique and machine quilting skills. Here are links to two that taught me a lot:
http://www.amazon.com/Mastering-Mach.../dp/157120136X
http://www.amazon.com/Heirloom-Machi.../dp/1571202366
She has a new series of skill building books out but I haven't seen them and don't know how they would compare to the above.