Salesforce recently hosted their annual developer conference, called TrailheaDX '17. The Salesforce Developers YouTube channel has posted a playlist of 138 videos from this awesome event.
The playlist is full of 40 to 60 minute video sessions and presentations. You'll see a lot of mentions of Einstein and Lightning, throughout. Here are some of my favorite videos from the list:
I hope you find something helpful in this list of free resources. Happy learning.