comScore put out its Q2 e-commerce sales estimates, and reported that e-commerce retail spending in the U.S. increased by 14% for the quarter compared to last year. Spending reached $37.5 billion.

That’s the seventh consecutive quarter of year-over-year growth.

“The second quarter of 2011 saw a continuation of this year’s solid double-digit growth trends in online spending, well ahead of the rate of growth in consumers’ overall spending,” said comScore chairman Gian Fulgoni.

“As a result, it’s clear that consumers are continuing to shift to the online channel, with almost $1 in every $10 of discretionary spending now occurring online,” he added. “E-commerce’s benefits of convenience and lower prices continue to be the drivers of the shift. At the same time, we are constantly reminded of an overall macroeconomic situation that is not indicative of a strong recovery.”

So what’s selling well online?

Consumer electronics, computer hardware and software and event tickets have been the top-performing categories. Each of these grew by at least 15%.

There’s some good news in the report regarding competition. The top 25 online retailer still accounted for the majority of spending (66.4%), but that number has gone down since the same period last year, when the top 25 accounted for 67.7%. The number peaked in Q3 2010 at 69.9%.

Interestingly, the growth in spending is due to more people buying online. The number of buyers was up 16% according to comScore, with 70% of Internet users making at least one online purchase in the quarter.

Don’t go throwing a party just yet though. Fulgoni thinks the third quarter may be more telling about where we’re headed.

“With economic growth remaining soft, the unemployment rate stubbornly high and financial markets in turmoil, consumers are less optimistic today than they have been in preceding quarters, which raises concerns for the future,” he said. “We believe the third quarter will be an important indicator of which direction this economy is really headed and what that will mean for consumer spending.”