Each morning, Arthur Marquis hears a familiar voice in his head. Yet it's the voice of someone he's never met.
It's a college professor speaking to his class and Arthur clings to every word of his lecture.
"The first one I started listening to was philosophy and literature and he went through various literary works including the Odyssey and the Iliad," Marquis said.
Arthur, like thousands of others, downloads the lectures directly into his iPod.
"They're really interesting," he said.
The best part is it's free. It used to be available only to students. But now, a growing number of universities are posting lectures on the internet. You can find them directly on school web sites, like openculture and a special section of iTunes known as iTunes U.
"Not only does it open things up to people who may never have had a chance to take classes like that, but it also means that you're getting access to something that has a real premium," said Melissa Perenson of PC World Magazine
Like a course in physics at MIT, a law class at the University of Pennsylvania, and a series on medicine at Stanford.
Hubert Dreyfus teaches philosophy at Berkeley. The phenomenon has made professors like him rock stars to an often unlikely audience. His lectures usually make the "top twenty" on iTunes.
"It makes me feel now that I'm being applauded all over. Poland, lately, France, Germany, England, just anywhere. That's what's so fascinating about it," Dreyfus said.
But there is a downside. Once Dreyfus started putting his lectures online, he found about a third of his students were often missing in class. It was almost enough to put a stop to posting until he started receiving letters from an "online student."
"Now at 41, I have discovered an incredible thirst for learning that has sparked a new passion and provides so much pleasure," wrote one student.
Marquis likes to listen to Professor Dreyfus while on the treadmill, to work out his body and mind.
"I enjoy it and it does make me see the world in a different way," Marquis said.
Apple says there have been more than six million downloads of iTunes U content since it debuted in the iTunes store on May 30.