Nielsen/NetRatings reported Monday that 11 percent of blog readers - visitors who claim to read blogs regularly or occasionally - use RSS to sort through the increasing number of blogs available. Specifically, nearly five percent of blog readers use feed aggregation software, and more than six percent use a feed aggregating website to monitor RSS feeds from blogs, according to Nielsen/NetRatings' "Understanding the Blogosphere" survey.

The vast majority of respondents were less familiar with RSS: 23 percent know about RSS but don't use it; 66 percent either do not understand it or have never heard of it - with the latter group constituting half of all respondents.

The number of unique visitors to the top 50 blogging and blog-related sites increased 31 percent, reaching 29.3 million, in July - compared with the beginning of the year. In other words, as of July nearly 20 percent of active online users had visited blogs.

In year-to-date unique visitor growth, MSN Spaces was first - with a 947 percent increase and nearly 3.3 million visitors in July, compared with 311,000 in January. Fark.com and Blogger ranked second and third, with 63 percent and 45 percent unique audience growth, respectively; fark had a unique audience of nearly 800,000 in July, whereas Blogger had 12.6 million.

Fourth through tenth in growth were Xanga, Daily Kos, Smoking Gun, Gawker, TypePad, engadget, and Boing Boing.