Tales of AdSense riches range from a few hundred dollars a month to $50,000 or more a year, though high-dollar paydays are rare. They require a Web site with tons of traffic and the ability to put in 18-hour days working the system.

Pirillo, who has a following from his former role as a host on the now-defunct TechTV cable channel, says he's clearing more than $10,000 a month.

Before AdSense, which began in March 2003, bloggers and other small Web publishers had fewer options to make money. They could put banner ads on their sites for a host of non-related products, or commission programs from Amazon and eBay. "It was a lot more work, and you didn't get much of a return," Pirillo says.

With AdSense, "You write content, publish it, and the money starts to pour in," he says.

When he published the now-defunct Silicon Alley Reporter magazine, Jason Calacanis says, he used to suffer from insomnia, worrying about his monthly $200,000 to $400,000 printing bill.

He now runs a company called Weblogs, which publishes 75 Web sites on such topics as cars, gadgets, digital music and video games. He sleeps much better, he says, because "with AdSense, you know you're always making money. Your life gets a lot easier."

In his first four months of Web publishing, AdSense brought in $45,000. Some of his blogs produce $3,000 a month. His best do "four figures," Calacanis says, though he's reluctant to fill in the exact numbers. "And that's with zero marketing," he says.