The company: SkinnyCorp, which owns online T-shirt retailer Threadless. Based in Chicago and founded in 2000, Threadless sells an estimated $30 million worth of graphic T-shirts a year by soliciting designs from a community of hundreds of thousands of amateur designers, who then vote on their favorites. Threadless bases production on the shirts that get the most votes and pays the winning designers $2,000.

The idea: Threadless CEO Tom Ryan and founder Jake Nickell thought that Twitter messages, because they are pithy, might work well as T-shirt slogans. In May, Threadless created a website that made it easy for the company's Twitter followers -- at the time, there were 490,000 of them -- to turn their favorite tweets into shirts. Users log on to a Threadless website,enter their Twitter username and password, and then submit tweets for consideration or vote on other people's tweets. The winning slogans get printed on T-shirts and sold for $18 each. "We figured if we built something on top of Twitter, we'd drive participation really quickly," Nickell says.

The result: Nickell was right. In its first five months, the Twitter experiment attracted 100,000 submissions and 3.5 million votes. So far, the company has printed and sold 23 designs -- "I'm huge on Twitter" and "Iowa: Cooler than California Since 2009" are the two most popular -- resulting in hundreds of thousands of dollars in additional revenue in the first five months. The promotion also helped Threadless add one million Twitter followers. "That's not bad for a brand-new product," says Ryan, adding that the Twitter Tees program also provided a revenue boost to Threadless's core business, as Twitter followers often stick around to buy other shirts.

How to get retweeted, Part I: Ask your followers for help -- and give them prizes when they comply. Nickell says one of the company's most successful tweets came when it offered Twitter followers a chance to win $100 if they passed along the news of a $9-per-T-shirt sale to their friends. The contest became one of the most popular topics on Twitter that day.