Каждый программист на javascript должен написать свою реализацию классов. ©

Dojo — dojotoolkit.org/reference-guide/dojo/declare.html#dojo-declare
Sencha (ExtJS) — www.rogerwilco.ru/2011/04/sencha-extjs.html
qooxdoo — qooxdoo.org/documentation/0.7/oo_feature_summary
MooTools — www.phpeveryday.com/articles/MooTools-Basic-Creating-Classes-MooTools-P919.html
Prototype — www.prototypejs.org/learn/class-inheritance
AtomJS — github.com/theshock/atomjs/blob/master/Docs/Class/Class.md
JSClass — jsclass.jcoglan.com/classes.html
code.google.com/p/jsclassextend/
github.com/jcoglan/js.class
Cobra — justin.harmonize.fm/index.php/2009/01/cobra-a-little-javascript-class-library/
github.com/JustinTulloss/cobra
The $class Library- www.uselesspickles.com/class_library/
Classy — classy.pocoo.org/
YUI 3 — www.yuiblog.com/blog/2010/01/06/inheritance-patterns-in-yui-3/
Coffee-Script — jashkenas.github.com/coffee-script/#classes
JavascriptClasses — code.google.com/p/javascript-classes/
AJS — amix.dk/blog/post/19038
jsFace — github.com/tannhu/jsface
JsOOP — jsoop.codeplex.com/
joot — code.google.com/p/joot/wiki/API
oopsjs — code.google.com/p/oopsjs/
Objs — github.com/tekool/objs/wiki
oorja — maxpert.github.com/oorja/
objx — code.google.com/p/objx/wiki/OClass
jsclassextend — code.google.com/p/jsclassextend/
prolificjs — code.google.com/p/prolificjs/wiki/OOP
objectize — code.google.com/p/objectize/

code.google.com/p/core-framework/wiki/Inheritance
code.google.com/p/sfjsoo/
code.google.com/p/jslproject/
code.google.com/p/magic-classes/wiki/MagicClassesOverview

github.com/ded/klass
github.com/jiem/my-class
github.com/kilhage/class.js
github.com/Jakobo/Sslac
github.com/BonsaiDen/neko.js
github.com/finscn/GT-Class
github.com/deadlyicon/klass.js
github.com/neuromantic/CodeJS
github.com/cj/js-oo
github.com/darthapo/klass.js
github.com/nemisj/zet.js
github.com/k33g/species
github.com/benekastah/JS-Class
github.com/tobeytailor/def.js
github.com/rstrobl/squeakyJS
github.com/shinyplasticbag/MojoClass
github.com/firejune/class
github.com/gcoguiec/jquery-class
github.com/daffl/JS.Class
github.com/pavelz/class.js
github.com/zerodogg/jqsimple-class
github.com/bnoguchi/class-js
github.com/arian/Klass
github.com/kuwabarahiroshi/joo
github.com/iamleppert/SimpleClass
github.com/aenoa/Noode.js
github.com/stomlinson/SuperClass
github.com/jzimmek/klazz
github.com/kbjr/class.js
github.com/jhnns/node.class
github.com/borysf/declare/blob/master/declare.js
github.com/ShadowCloud/BF-Class
github.com/pic-o/jsClass
github.com/rosamez/jquery.klass
github.com/yuki-kimoto/javascript-Class_Simple
github.com/yaksnrainbows/jarb
github.com/thirashima/UnderClass
github.com/arahaya/package.js
github.com/arieh/Class.def
github.com/bogdan-dumitru/jsClass
github.com/pomke/pomke.js
github.com/sgolasch/jClassify
github.com/kbjr/Classy
github.com/cthackers/jClass
github.com/davidjbeveridge/Clasico
github.com/edave64/protojazz
github.com/mrac/solid.js
github.com/benekastah/Classy
github.com/damianmr/JSMiniClass
github.com/benekastah/classesWithCash
github.com/dialog/Resig-Class
github.com/mpodriezov/OJS
github.com/dtinth/twcs.js
github.com/percyhanna/js-class
github.com/jalopez/SimpleClassJS
github.com/jhamlet/proteus
github.com/petebrowne/classify
github.com/TdroL/Classy.js
github.com/azendal/neon
github.com/aulizko/Alan-Point-JavaScript-Library/tree/master/src/oop