I compiled a list of IMHO great examples of social media used for causes for a friend who works at a foundation exploring how to fund this area. Thought it was relevant enough to put out there on the blog. Post your examples as well.

1. Facebook: I could say a lot about how nonprofits can and cannot use Facebook as part of their strategies. In some ways, the parts of Facebook that have been developed for organizing on Facebook are the worst parts of it. Groups and Causes both lack just about every tool that makes organizing in the 21st century so powerful. However, it is the other aspects of Facebook that allow us to connect to friends so powerfully that causes and nonprofits are starting to really utilize, particularly donate your status or profile picture campaigns and to a lesser degree events.
2. SMS: Obama’s SMS campaign was used in the way that it can work. SMS is a highly personalized mode of communication. It is only those with whom you want to be most intimate with that you want to text with. People wanted to be closer to Barak Obama, and SMS messages enabled that to a degree never before seen.
3. Creative Fundraising: A group of Ron Paul supporters that had nothing to do with the campaign, organized an online fund-raiser on Guy Fawkes Day, bringing in more than $4 million and 21,000 new contributors in a single day — the largest 24-hour haul of any Republican candidate to date. The key word here is creative. Not fundraising.
4. Video: I may be a little biased here, but Students for a Free Tibet has done some great video work—from instant satellite uploads of nonviolent civil disobedience and banner hangs inside Tibet and China to updates to their communities to on the spot interviews with government officials. They even created their own internet television station during the Olympics where you could get news updates, see profiles on the activists who were getting arrested, see movies on Tibet, etc.
5. Viral Video: The Great Schlep was a classic example of brilliantly executed video with all of the makings to go viral. 1.25 million views on You Tube alone.
6. A bad example: I love the folks at moveon.org, but I think that it is an outdated model for how to use social media to advance causes. Their system is not really participatory in the way that the Obama campaign proved is possible—moveon.org members vote on a set number of initiatives or videos. Obama’s myBO.com gave people the ability to create their own campaign and implement it, not just push a prescribed one developed by professional staffers. What moveon.org’s system IS really good at is rapid response to an important and timely issue or opportunity. The moveon.org system also doesn’t allow its members to know each other and self organize. It is almost too dependant online, and hasn’t translated to offline, which to me is an important indicator of a successful social media tool.

An article that outlines some great social media used for causes

The NY Times also did an extensive article this weekend on how Egyptian youth used Facebook to organize. It highlights that social network sites like Facebook are hard for repressive regimes to identify as activist threats and shut down. "[A]round the world, dissidents thrive on sites, like Facebook, that are used primarily for more mundane purposes (like exchanging pictures of cute cats). Authoritarian regimes can’t block political Facebook groups without blocking all the “American Idol” fans and cat lovers as well. “The government can’t simply shut down Facebook, because doing so would alert a large group of people who they can’t afford to radicalize,” Zuckerman explained."

Other State Department officials told me they believe that social-networking software like Facebook’s has the potential to become a powerful pro-democracy tool. They pointed to recent developments in Saudi Arabia, where in November a Facebook group helped organize a national hunger strike against the kingdom’s imprisonment of political opponents, and in Colombia, where activists last February used Facebook to organize one of the largest protests ever held in that country, a nationwide series of demonstrations against the FARC insurgency. Not long ago, the State Department created its own group on Facebook called “Alliance of Youth Movements,” a coalition of groups from a dozen countries who use Facebook for political organizing. Last month, they brought an international collection of young online political activists, including one from the April 6 group, as well as Facebook executives and representatives from Google and MTV, to New York for a three-day conference.

Lastly, I'll just throw in a couple of interesting quotes:

Communities are sticky in ways that mass media never was, it requires a very different approach to what we create, how we create it and how we market it.
Yochai Benkler, Wealth of Networks

In the new and evolving online world, the greatest momentum goes not to the candidate with the most detailed plan for conquering the Web but to the candidate who surrenders his own image to the clicking masses

Such developments probably came as no surprise to many in the business world, who understood years ago that the Web represented not simply another mass medium to be gamed but also a fundamental shift in the once static relationship between producer and consumer. It is by nature a participatory medium, in which customers demand a more personal stake in the products they consume.
Matt Bai, NY Times writer + author of “The Argument: Billionaires, Bloggers and the Battle to Remake Democratic Politics"