Prototype-based

Agora
OO prototype-based, reflective language, based on only message passing, a key trait of OO languages; it allows late-binding polymorphism, the key trait making possible incremental modifying of programs. Descriptions, papers, implementations: Smalltalk, C++, Java, Scheme; MiniMix.
http://prog.vub.ac.be/research/agora/

Brain
High-level, pure object-oriented, prototype-based, scripting language; Smalltalk-like syntax; some features borrowed from Scheme, Self, JavaScript. [Open Source, LGPL]
http://brain.sourceforge.net/

Glyphic Script, Codeworks
Language with interactive development environment, supports multiple views per object, bytecode VM; was user programming environment of EO communicator; description, PDF manuals. By Mark Lentczner.
http://www.ozonehouse.com/mark/codeworks.html

Isaac Project
Small prototype-based high-level language, influences: Smalltalk (all values are objects), Self (prototypes), Eiffel (Design by Contract); allows system, low-level programming, compiler has means for late binding suppression, optimizing type predictions and code specialization, gives target code high efficiency.
http://isaacos.loria.fr/li.html

Lisaac
Small, fast language inspired by Smalltalk, Self, Eiffel (design by contract); auto-cast static typing, multiple inheritance. Part of Isaac prototype-based OS. Description, downloads, library, benchmarks, code samples.
http://isaacproject.u-strasbg.fr/li.html

Mica
Was Poe: prototype inheritance language and OO virtual machine for building network-accessible programs for multiple programmers, users, agents. Persistence and garbage collection are automatic and transparent. [Open Source, GPL]
http://sourceforge.net/projects/coolcc/

MLud
A runtime-extensible language built on top of SML/NJ designed for building collaborative environments. Supports dynamic delegation with multiple dispatch, several useful datatypes, inline ML, and checkpoint persistence.
http://moonflare.com/code/mlud/

Object-based PLs
By Rainer Blome. Alphabetized list with descriptions of, and links to, many prototype-based languages.
http://www.pasteur.fr/~letondal/object-based.html

OScheme
Small, embeddable interpreter, mostly Scheme R4RS compliant, with extensions: supports prototype-based object model, some POSIX system calls, compilable in secure mode. Description, download, links.
http://koala.ilog.fr/abaird/oscheme/oscheme.html

Prototype-based Programming
Growing article, with links to many related topics. [Wikipedia]
http://en.wikipedia.org/wiki/Prototype-based_programming

Slate
Language-OS based on CLOS, Self, Smalltalk; Smalltalk syntax; libraries inspired by Common Lisp, Dylan, Strongtalk (strong typing). Descriptions, programming manual, tutorials, summaries, bulletin board Swiki, CVS. [Open Source, LGPL]
http://slate.tunes.org/

The Slate Programming Language
Brief description with many forum comments. [Slashdot] <small>(March 27, 2004)</small>
http://slashdot.org/developers/04/03/27/1627220.shtml

Class-based NewtonScript Programming
An article for PIE Developers magazine describing a technique for structuring a NewtonScript program using class-like objects. <small>(January, 1994)</small>
http://waltersmith.us/wp-content/uploads/2005/12/class-based-NS.htm