Aurelia seems to be the best ideas from Angular + the best ideas from the creator's previous framework, Durandal, in one framework with much cleaner syntax and much less complexity than both Angular & Angular 2.0.
Ember has made some big updates recently, rewriting their rendering engine to use a virtual DOM.
A lot of people still seem to really like Meteor.
Mercury, Mithril, Ractive, JSBlocks, etc. are all smaller, lesser known projects with a lot of potential.