The content of the Internet, and who is creating it, is changing.

In its latest tracking data on fast-growing Web sites, covering July 2006, Nielsen//NetRatings found that user-generated content sites (platforms for photo sharing, video sharing and blogging) comprise five out of the top 10 fastest-growing Web brands.

Image-hosting site ImageShack ranks fourth among the fastest-growing Web brands, increasing 233% between July 2005 and July 2006, from a unique audience of 2.3 million to 7.7 million., a video-sharing site, is No. 5, increasing 213%, from 965,000 to 3 million unique visitors. Photo-sharing site Flickr is next on the list, growing 201%, from 2.1 million to 6.3 million unique visitors.

"User-generated content sites have seen significant growth over the past year, owing in large part to their reliance on viral marketing," said Jon Gibs of Nielsen//NetRatings. "They also benefit from their cost-effectiveness — the content is practically free."

Among the top 10 Web brands overall, MySpace is the fastest growing, increasing 183%, from 16.2 million unique visitors in July 2005 to 46.0 million in July 2006. Google ranks second, growing 23%, from a unique audience of 76.2 million to 94.0 million, and eBay rounds out the top three, increasing 13%, from 51.1 million to 57.8 million unique visitors.

"MySpace is in a nearly unique position, because of its large audience base and its continued triple-digit growth," said Mr. Gibs. "Only other popular user-generated content sites, such as YouTube, can rival it."

"The continued growth of MySpace and other user-generated content sites shows that Web users are eager to let their voices be heard," said Debra Aho Williamson, eMarketer senior analyst. "If these trends continue, the makeup of the Web’s top 10 destinations could look very different in the coming months and years."

More here.