Ideally, I'd like to create a stand-alone Angular 2 component (with tests) and then re-use it between two or three different Angular 2 sites. What are the good ways to achieve this? And a bonus question - do any 3rd party Angular 2 components exist?
UPDATE
OFFICIAL Angular CLI https://angular.io/guide/creating-libraries
You can create an angular2 component library (with tests) and then use it in any number of projects
Here's how to create an angular2 library https://makina-corpus.com/blog/metier/2017/how-to-create-an-angular-library
with angular-cli https://medium.com/@nikolasleblanc/building-an-angular-4-component-library-with-the-angular-cli-and-ng-packagr-53b2ade0701e
Then you can publish it for public use as well. If you want to keep it private, you can read this https://www.npmjs.com/onsite
Yes, many 3rd party angular2 components exist. Here are few from valor-software https://github.com/valor-software/ng2-plans
Yeoman Generator for angular library https://github.com/jvandemo/generator-angular2-library