Apart from the marketing hype it is still surprisingly hard to find real word examples and tips concerning Dynamics 365, PowerApps and Flow. These two sites offer tons of information, great work:
Short recap of the edX course Developing Business Applications with Power Apps and Microsoft Flow
The course was a great starting point for me. The video tutorials are short but nevertheless full of information. I also found the labs interesting and fun.
The course is outdated regarding user interface and especially the parts dealing with CDS (old version 1.0 in tutorial).
What a great day at Microsoft Zürich, I was happy to attend the Train the Trainers PowerApps partner workshop:
Canvas app design vs. model driven:
And if you want to get started with PowerApps this great tutorial will help you a lot