I just stumbled across dart again.
It really got me interested and I started digging into resources.
Here’s what I’ve found so far.

I’ll add more as far as it helps me.

Websites

https://www.dartlang.org
https://www.dartlang.org/articles/dart-unit-tests

Videos

After you got an overview, maybe you want to dig deeper into dart. Try these quick video tutorials.
https://www.dartlang.org/dart-tips