Online shopping is increasingly popular in the US, according to comScore. The data outfit reports today that online spending rose 9% in the third quarter, totaling $32.1 billion and marking the fourth straight quarter of year-over-year growth. The yearlong increase follows a patchy period between Q4 2008 and Q3 2009 when spending fell by 6%.

The most active product categories were Books & Magazines (excluding digital downloads), Computers/Peripherals/PDAs, Computer Software (excluding games), and Consumer Electronics. Interestingly, the top 25 e-tailers represented 70% of dollars spent online, up 5.5% from last year, and 41% of purchases included free shipping, down "marginally" from 2009.

ComScore chairman Gian Fulgoni says the results are a "fairly positive indicator for the upcoming holiday season," but warned that unemployment is still high and even those with jobs are spending carefully. "Until the economy begins adding jobs at a meaningful rate, the lack of spending power among consumers will continue to be a drag on purchasing, with many consumers indicating their intention to cut back on gift buying this holiday season."