A great example of a collaborative website driving a business, Threadless http://www.threadless.com lets users design t-shirts, vote on popular styles, and then buy most popular shirts produced by the company. "Naked no more."
Jigsaw allows users to pool contacts databases, requiring they either pay $25 / month or contribute 25 names. http://www.jigsaw.com.
A detailed and well designed reputation and ranking system designed to encourage participation and good behavior. Details athttp://answers.yahoo.com/info/scoring_system
Google offers advertisers the chance to update billboards in Google StreetView -- and will sell unclaimed inventory .http://ow.ly/VlEM
Immunet protects social networks from viruses through monitoring the crowd.http://bit.ly/7tyN4h
Google and Facebook present different versions of politically sensitive maps, depending on which user is requesting. http://ow.ly/wrgk
eJamming allows users from around the globe to find one another for real-time jam sessions. Forbes "breakout" idea of 2009. http://eJamming.com
Coca Cola has selected three hip, photogenic "happiness ambassadors" to travel the world as social media ambassadors. http://ow.ly/DlSW
"Peace on Facebook", a section which show how many friendships are occurring across lines of conflict, offers a glimpse on what the social networking site could provide towards world peace. http://ow.ly/EjfW
Large financial investigations (like AIG) are costly to conduct. Put the financials online and let interested parties assist. http://ow.ly/NVlA
With so many barriers to communications in the Middle East, efforts should be made to push more dialogue into convenient social media channels. http://bit.ly/6nVjzs
A number of iPhone applications allow users to help charitable causes with periodic moments of free time. See, for example, The Extraordinaries http://www.beextra.org
Supporting social networks globally - but not telling people how to use them - is in the strategic interest of the US. http://www.nytimes.com/projects/magazine/ideas/2009/#s