The comScore Media Metrix monthly analysis of U.S. consumer activity at top online properties for March 2007 has been released, and shows a change at the top of the rankings. Several key players in the social networking space experienced gains, as did those looking to both make and save money who flocked to lotto and coupon sites, while Coca-Cola’s “My Coke Rewards” promotion spurred a 40-percent increase to the Coca-Cola Company property, which saw nearly 5 million visitors in March.

“Shifts at the top of our Ad Focus ranking come at an interesting time with Google’s recent announcement that it would be acquiring Doubleclick,” Jack Flanagan, executive vice president of comScore Media Metrix told DaniWeb, continuing “As advertising networks continue to compete for online ad dollars, there is sure to be increased attention on which ones are reaching the widest audience.”

When it comes to social networking and video sharing sites, the top gaining properties were which surged 25 percent, and eight spots in the Top 50 ranking, to nearly 21 million visitors and, which grew 60 percent versus February to 6 million visitors. Heavy Networks was the month’s top gaining property, up 100 percent to 6.8 million visitors, driven in large part by a popular video spoof featuring Pamela Anderson as a cartoon superhero, while traffic to video site Metacafe surged 40 percent to 5.6 million visitors

In the March Top 50 Properties Ranking, Yahoo! Sites remained at number one, while Microsoft Sites gained one spot, capturing the number three position. Wikipedia Sites also moved up a spot to number eight with more than 47 million unique visitors in March. Beyond the top ten, Idearc Media enjoyed a 43-percent increase in claiming the number 27 spot. Other top movers included, which gained eight spots to number 28, and ESPN, jumped 12 positions to number 33 with 19 million visitors, attracting heavy interest with its NCAA tournament coverage. Within the Ad Focus Ranking, March saw reach 86 percent of the U.S. online population, while Yahoo! inched up a spot to claim the number two position. Nickelodeon Kids & Family and Network both moved into the ranking in March, reaching 12 percent and 10 percent of the U.S. online population, respectively. Finally, CPX Interactive jumped eleven positions to number 18 in the ranking, reaching more than 76 million Americans.