Superheroic

Micro.js, combined.

Utils

Toolbelt: http://underscorejs.org / http://lodash.com
Functions: https://github.com/raganwald/allong.es
Async: https://github.com/caolan/async
Promises: https://github.com/tildeio/rsvp.js
Events: https://github.com/Wolfy87/EventEmitter

Types

URLs: https://github.com/websanova/js-url
Strings: http://epeli.github.com/underscore.string/
Numbers: https://github.com/josscrowcroft/accounting.js
Dates: http://momentjs.com/

Compat

HTML5: https://github.com/aFarkas/html5shiv
Normalize CSS: http://necolas.github.com/normalize.css/
ES5: https://github.com/kriskowal/es5-shim
JSON: https://github.com/douglascrockford/JSON-js
Media queries: https://github.com/scottjehl/Respond

Data

Models: ...
Collections: ...
Storage: https://github.com/marcuswestin/store.js
Cookies: https://github.com/js-coder/cookie.js
Ajax: ...
Sockets: ...

Browser & DOM

Routing: https://github.com/olav/dispatch.js
Bindings: http://rivetsjs.com/
Touch events: http://quojs.tapquo.com/
Creation: https://github.com/markgandolfo/el.js

Build

Syntax: http://www.jshint.com/
Minification: ...
Testing: ...

See also