I stumbled upon some excellent training resources on YouTube created by Dick Rochfort of RWR Pilot Training. He just posted a very detailed one on the GTN650 today. He also has a number of in-flight videos demonstrating real-world use of a variety of avionics. Specializes in PA46 (Malibu/Matrix/Meridian) training all over the world. Good stuff.
http://www.youtube.com/user/rwrpilottraining?feature=watch
http://www.youtube.com/user/rwrpilottraining?feature=watch