What's the easiest money in pro sports? Twitter.

A month after announcing his retirement – on a Twitter-linked video that shot across the planet – Shaquille O'Neal and his marketing squad welcomed 30 brand executives into his Orlando, Florida, home. After touring Shaq's Bentley collection and indoor basketball court, they settled into his massive living room to talk about his future as a pitchman. The suits from Oreo, Icy Hot, and Toys "R" Us talked about the usual partnerships – television, print ads, and live events in which the NBA star could draw crowds. But the main topic of discussion was Twitter.

"I never say 'Go buy this' on my Twitter," says Shaq, explaining how his approach to social media can work for corporate America. "I make people laugh – I inspire people. I have a deal with Oreos. I do a shout-out, saying, 'I'm eating Oreos. How many can I eat in 15 seconds?' And that makes you laugh – you talk about Oreos, and then 10 percent of the four million people go buy Oreos." For Shaq, who already makes around $15 million a year on traditional endorsements, those shout-outs are big money and, according to his media strategists, could earn him an extra $1 million to $5 million, thanks to his 7.7 million Twitter minions.

Players who can build Twitter followings – such as Shaq; Chad Johnson, formerly Ochocinco (3.7 million followers); and Terrell Owens (1.3 million) – are finding that Twitter is a cash register filled with sponsors; all they need to do is tell their fans, in 140 characters, to buy Oreos, pick up their Madden video game, or go to a nightclub. Sometimes the tweets are requirements laid out in an endorsement deal. But often they come from the fast-growing pay-per-tweet market. Here's how it works: A player talks to McDonald's ad execs about a onetime deal, tweets about their new wraps, and, bam, there's a $10,000 check in the mail.

Ryan Steelberg, CEO of the company that owns Fantapper, a Web portal that works with 3,700-plus professional athletes, in addition to celebrities, values them all on a 20-point data system, counting among other things the number of times their name appears in print. Two years ago, as Drew Brees, quarterback of the New Orleans Saints – 2009 Super Bowl champions – headed into the play-offs, he closed a $15,000 deal to send an e-mail blast about a national florist to his fans. "Endorsement deals can take months," says Steelberg. On this deal, "Drew did almost nothing, just click and send," he adds. Brees has since landed similar deals on Twitter, thanks to his 1.7 million followers.

In the past few years, athletes have jumped on Twitter as a way to talk directly to fans – bypassing SportsCenter and local reporters – to give their take on last night's game, ask fans for their opinions, and even share details about their workouts or home lives. All of this has made fans feel closer to favorite players. The NBA's Dwight Howard has even invited a few Twitter fans to dinner.

But adding paid ads to the feed – written as if they were straight from the mouth of the player – has spoiled the intimacy of some Twitter accounts. Chad Johnson is among the busiest sponsored tweeters; his tweets are often a blurred, or just clumsy, endorsement. Here's one multibrand post from this past September: "Love is a mothaf*cka, makes you wake up in the middle of the night to make Peaches n Cream oatmeal with a glass of Simply Orange OJ." Shaq's social media adviser, Amy Jo Martin, who also represents UFC, Fox Sports, and the Chicago White Sox, discourages athletes from the pay-per-tweet model, pushing them to develop their own brands by sharing genuine information about their lives and building long-term, new- and old-media endorsement deals. Even Shaq – who shoots 15-second videos of himself doing stunts for fans – says he's put off by too much self-promotion by his peers. "A lot of guys use it to big themselves up," says Shaq. "I don't want to see your car or your chain. I don't want to see every three minutes of your life. Get rid of your chain – show me a karate move." Of course, not all of Shaq's tweets are such subtle entertainment: "Even [though] I'm retired, I'm still dunkin',?" Shaq wrote in a tweet in June. "Get a signed [pack] of Triple Double Oreos and help."

When athletes hire third parties to write tweets for advertising dollars, the result is an even faster, less personal buck. The pay-for-tweet outfit Adly writes sponsored tweets in the voice of its clients, who then send those out to their fans. The blasts end with the hashtag #ad to indicate they are paid advertisements, and sound and read like professional advertising. Buffalo Bills linebacker Kirk Morrison (with 345,000 Twitter followers), Yankees outfielder Nick Swisher (1.68 million followers), tennis all-star Serena Williams (4 million), and world-champion boxer Floyd Mayweather (4.5 million) all work with Adly and use the #ad tag with some regularity.

The embrace of sponsorship has not been warmly felt by all. Skateboarder Tony Hawk lost a couple of deals, including one with a big electronics company, because he refused to tweet their words as his own. "If I have a sponsor requirement to tweet, I tell them I'm not gonna put it out verbatim, because there's no heart in it," he says. With 3.5 million followers, Hawk is one of the most followed athletes on Twitter and a potentially valuable pitchman. Brands like Fender guitars, Kicker headphones, and Activision video games have participated in treasure hunts he announces on Twitter. And while his audience helps him get "good money" for his X Games commentary on ESPN, he doesn't do many sponsored tweets. One sponsorship he does take on is for a boutique hotel in Los Angeles – for barter. "They give me really sweet deals if I promise to tweet about them," Hawk says. "I get a suite for a discounted rate. It's not a source of revenue, but it's a perk."