Among the hottest courses in what Apple bills as the world's largest online catalog
FORTUNE -- In a press release issued Thursday, Apple (AAPL) announced that content from its iTunes U site has been downloaded more than 1 billion times since the free educational service launched in May 2007.
There are now individual classes with more than 250,000 students enrolled in them, according to Eddy Cue, the senior VP in charge of MORE
