Pinterest is the social network with all the buzz these days, and it sounds like all the attention is warranted: a new study from Experian suggests that Pinterest is the third most popular social network, just behind Twitter and Facebook.

Experian’s “2012 Digital Marketer: Benchmark and Trend Report” shows new highs for social media. Social networking is the number one internet-based activity for 15 percent of US households, and 91 percent of US adults use social networks regularly.

And it’s Pinterest that stands out among even the social media stalwarts. With traffic up 50% between January and February 2012, Pinterest has become the third most popular US social network. It received just about 21.5 million total visits during the week ending on January 28 2012, which is 30 times the number of total visits just six months ago.

Pinterest has beat out LinkedIn, Google+ and a whole host of other social networks for third place, behind only Twitter and Facebook – networks that have more than 5 years’ head start on the photo-heavy network.

But, of course, it’s Facebook that still leads the pack. More than 50 percent of online adults use Facebook regularly, making it the number one social network by far. One in ten of all US internet visits is to Facebook, and it captures one in five page views. It’s also poised to break the 1 billion user mark this year.

Still, Twitter is growing, as are Google+ and LinkedIn. Twitter saw 45 percent growth between December 2010 and December 2011, LinkedIn grew 98 percent in this same time period, and Google+ exploded by more than 800 percent between August 2011 and December 2011.

The report suggests that all of this social media growth is affecting our purchasing behavior, and those brands with a big social presence are much more likely to capture users’ attention. For instance, social media users are more likely to fly Virgin Atlantic airlines, own an iPhone, visit Starbucks and play Nintendo DS than their non-social counterparts.

You can read the full report here.