Unique visitors to the sites included in the Index reached 35.9 million, a 13% increase over this year’s Black Friday Web traffic.

Many of the top online retail destinations on Cyber Monday were the same as those on Black Friday. eBay drew the largest unique audience (10.6 million), while Amazon and Wal-Mart claimed second and third places, with 9 million and 5.2 million unique visitors, respectively.

Among the top 10 online retailers, Sears’ site saw the fastest growth (+58%, year over year).

Beauty was the fastest growing product category on Monday, increasing 151% over the previous Monday, November 24, 2008.

Toys/Videogames ranked second, growing 112% Monday over Monday, while Apparel rounded out the top three with an increase of 58%.

“The growth in traffic to online retail sites on Cyber Monday was better than many people expected, making retailers hopeful that this growth will carry through the holiday shopping season and drive sales,” Ken Cassar, vice president, industry insights, Nielsen Online, noted.  “It remains to be seen if people have done the majority of their shopping on these two big shopping days to save time, or if they are holding out for additional sales and promotions. If history is any indication, we expect that Monday, Dec. 15th will be the peak day for online shopping traffic.”

View the full press release.

Read coverage of Nielsen’s findings by the Associated Press and Bloomberg, as well as in The Wall Street Journal, the Financial Times, Investor’s Business Daily, Ad Age, PC World, the Orlando Sentinel, ClickZ.com, and InternetRetailer.com.