Last week, U.S. news organization USA Today launched a four-day Twitter hashtag campaign for charity. The grand prize? A full-page, full-color ad in USA Today, valued at $189,400.

The charity that had the most retweets of the message “#AmericanWants [charity name] to get a full-page ad in USA TODAY” with its name in the tweet between Tuesday, April 13 and Friday, April 16 was declared the victor.

This afternoon, USA Today announced the winner, To Write Love on Her Arms, a four-year-old non-profit dedicated to helping those struggling with depression, addiction, self-injury and suicide. Founder Jamie Tworkowski (pictured above) said that the organization found out about the contest right around the time it launched. “A few of us were awake and knew we had to jump on it,” Tworkowski told USA Today. “We tweeted [to our 77,164 followers] right away, got something up on the website, and started making noise.” People for the Ethical Treatment of Animals (PETA) was the runner up.

In all, users posted more than 60,000 tweets in support of more than 500 organizations. The tweets reached an estimated 67 million users on Twitter, according to data collected by Radian6.

The #AmericaWants hashtag contest was conceived by Social Media Strategist Alex Nicholson as part of USA Today’s larger “What America Wants” brand campaign, designed to illustrate USA Today’s connection with the American experience and readers’ engagement with the brand on multiple media platforms.

The contest is similar to another campaign USA Today put on in 2007, “Spirit of the USA,” which provided free media to 25 charities in roughly 25 weeks. The primary difference between the 2010 campaign and the 2007 campaign is the use of Twitter to spread the message. Susan Lavington, senior vice president of marketing, said that USA Today plans to “evolve the idea again.”

We’ve heard of some great charitable campaigns on Twitter before, but few with this much reach. What are some of the social media campaigns for charity you’ve heard about or participated in? Please share with us in the comments.

For more social media coverage, follow Mashable Social Media on Twitter or become a fan on Facebook

Reviews: Facebook, Radian6, Twitter

Tags: charity, social good, social media, twitter, usa today