Does any one have recommendations for a online Music introduction/Appreciation course?

How old is your child? Mine was very interested in classical music from an early age and I used the resources from Classical Kids - http://www.classicalkidsnfp.org/shop/
There are also movies in DVDs available that matches the Classical Kids CDs which are very good.
Beyond that, we read a lot of books about composers and always had classical music playing in the background in the house and the car. Our local classical music station also talks about composers and little trivia about them and their times before playing each piece which tremendously helped my child learn about music history.

Hi Ashley, kids are 10 and 8. For was looking for more of an online course. There is one from CTY but my kids are already beyond that.

DS and I are currently doing this free course from Stanford: http://online.stanford.edu/course/defining-string-quartet-haydn

Have you looked into Coursera?

I vaguely remember a music theory course that came highly recommended but I can't find it now. This course looks good:

https://www.coursera.org/learn/introclassicalmusic

Mana this seems exactly what I am looking for. Just need to figure out if this is kid-friendly enough.

Ashley, the string quartet course seems like a great option for a kid playing in one. Does your DS do so?

Yes, my son plays the violin in a string quartet. He likes this course (but, he is the kind of kid who easily likes most online courses )