The big news this week is Dart going into BETA - congratulations to all the team for reaching this important milestone!
The release notes carry all the detail. There's been a big focus on performance with dart2js, Dart VM and the Dart Editor all getting boosts. (Given I am currently developing a HTML5 game in Dart on an Atom netbook, I was very pleased to hear this!)
On pub.dartlang.org there is an interesting weather package - weather_underground_api