A small sampling of external projects initially built for Ember use but designed to be used standalone:

* [Handlebars](https://github.com/wycats/handlebars.js) - templating engine
* [simple-html-tokenizer](https://github.com/tildeio/simple-html-tokenizer) - an HTML5 tokenizer
* [HTMLBars](https://github.com/tildeio/htmlbars) - alternate HTML-aware Handlebars backend
* [morph](https://github.com/tildeio/htmlbars/tree/master/packages/morph) - text-node placeholders for data binding systems
* [RSVP](https://github.com/tildeio/rsvp.js) - fast, lightweight promise library
* [route-recognizer](https://github.com/tildeio/route-recognizer) - just the recognition part of a router
* [router.js](https://github.com/tildeio/router.js) - hierarchical states and transition-based router
* [dag-map](https://github.com/krisselden/dag-map) - graph library
* [backburner](https://github.com/ebryn/backburner.js) - Ember's "run loop"
* [broccoli](https://github.com/broccolijs/broccoli) - minimal tree-based build pipeline
* [loader.js](https://github.com/stefanpenner/loader.js) - minimal AMD loader

Ember itself is broken into [many pieces](https://github.com/emberjs/ember.js/tree/master/packages), among them:

* metal - Ember's mixin system with observation/property support, works on bare POJOs
* runtime - Ember's object model (depends on `metal`)
* container - Ember's dependency injection container (depends on `metal`)
* views - the basic Ember view layer, agnostic to templating (depends on `runtime`)
* handlebars - builds on Ember's core view layer with templating support
* application - Ember's application bootstrapping
* routing - adds Ember view and application integration to router.js
* debug / testing - Ember functionality that makes sense in specific environments