Unless you're a member of the Dart misc group, you may be missing Florian Loitsch's weekly newsletters, which started in July. They live in the SDK repo (docs/newsletter), but Florian also posts them in the misc group.
These newsletters cover the Dart language and some of the core libraries. Read them to learn about existing features ("Did you know"), planned changes, and how the Dart team considers and implements changes. For example:
The July 28 newsletter (the first) starts with some 1.24 language changes that you might have missed: function types and changes to void. It also talks about the unified front end, and what that means for language changes. Finally, the letter lists features in active development, such as zones that work well with strong mode, void as a type, and changes to the core libraries.
The September 29 newsletter covers 1.x JSON encoding, and plans for fixed-size integers.
The October 13 newsletter covers 1.x double.toString methods and planned changes to evaluation order. It also describes why even simple language and library changes require so much thought, and why they often take so much time.