Wikipedia defines collaboration as follows :

Collaboration (co+labor+ation) refers abstractly to all processes wherein people work together - applying both to the work of individuals as well as larger collectives and societies. As an intrinsic aspect of human society, the term is used in many varying contexts such as science, art, education, and business.

Reference Material

Co-Creation Rules! by James Cherkoff and Johnnie Moore

The Wisdom of Crowds by James Surowiecki

Networked computing comes of age by Steve Lohr

Democratizing Innovation by Eric von Hippel

Presentation on Democratizing Innovation by Eric von Hippel

Geeks in Toyland by Brendan I. Koerner

The rise of Crowdsourcing by Jeff Howe

The Wealth of Networks by Yochai Benkler

Crowdsourcing book project by Jeff Howe

Politics and Media in the Internet Age by George Osborne

The significance of Threadless.com by Tim O’Reilly

Giving it away by Cory Doctorow

Open Source Spying by Clive Thompson

Wikia unveils OpenServing press release

Tech lessons learned from the wisdom of the crowds by Declan McCullagh

Person of the Year : You by Lev Grossman

Wikinomics could change everything as concept spreads by Russ Juskalian

Pick better stocks with Stockpickr by James Altucher

The BusinessWeek Wikinomics Series by Don Tapscott and Anthony Williams

Getting rich off those who work for free by Justin Fox

The Hotel That Time Built : The Rejenerated Dante Hotel by SLH

Volunteers sign up to build game by Darren Waters

The rise and fall of corporate R&D by the Economist

Virtual space gurus build final frontier by Alan Boyle

Young scientists design open-source program at NASA by Aaron Rowe

The One Million Masterpiece - the worlds largest artistic collaboration

Dell quells critics with Web 2.0 tack by Matthew Creamer

Whos writing the book of the net? by Victor Keegan

They’re working on their own, just side by side by Dan Fost

Social Collaboration Services

Aftervote : search engine

Amie Street : music

3D Warehouse : 3D models

37 Signals : organization

ChaCha : search engine

ChangeThis : publishing

Crowdstorm : social shopping

Cucumis : translation

Dabble : video search

Dandelife : real stories

Dell Idea Storm : ideas

Doodleboard : drawing

dotSUB : video subtitles

Horsesmouth : mentoring

eJamming : music

Fliptrack : music

Kiva : loans that change lives

Lego Factory : custom Lego models

Mahalo : search engine

My Currency : real estate valuations

Ourstory : stories about life

Outside.In : neighborhood conversation tracker

PicksPal : predictive sports results

Plum : collect, share, connect

Prosper : people-to-people lending

SourceForge.net : Open Source software development

Stockpickr : Stock idea network

Superviva : life lists

Threadless : designer clothing submissions

Wasabe : financial advice

Wikia : community of communities

Yahoo Answers : community-driven Q&A

Yahoo Suggestion Board : suggestions

Yelp : real people, real reviews

Zebo : what people own

Zecco : stock trading and investment

Zimbio : peoples guide to the web

Zopa : lending and borrowing exchange