Dueling reports Wednesday from the two leading PC survey firms — Gartner and IDC — confirm what the crowds at the Apple (AAPL) stores have been telling us: The Mac had a great second quarter.

According to Gartner, Mac sales grew 38% year-over-year to edge out Acer/Gateway/PackardBell for the No. 3 spot in the United States after Dell (DELL) and HP (HPQ). IDC recorded slightly slower growth (31.7%) and has Apple still trailing Acer by 2,000 units — not a statistically significant figure in a quarter in which Apple shipped an estimated 2.37 million Macs worldwide.

Gartner puts Apple’s U.S. market share at 8.5%, up from 6.4% a year ago; IDC has it at 7.8%, up from 6.2%. Both reports are preliminary.

Apple still doesn’t make the top 5 in either company’s list of top PC vendors worldwide, although IDC’s Loren Loverde says it came in No. 6. (link)

It’s worth noting that while its competitors were cutting prices to boost sales in a tight domestic economy, Apple managed to grow faster while maintaining profit margins that are the envy of the industry.

And if you count iPhones and iPod touches as computers, says 9to5 Mac’s Seth Weintraub, “you get a whole new ball game.”

Below the fold: the charts from both reports.

Microsoft (MSFT) Windows continued its downward drift and Apple’s (AAPL) Mac OS X inched up to a record 7.95% in the market share survey issued Tuesday by Aliso Viejo, Calif.-based Net Applications.

The biggest gain, however, was recorded by the open-source operating system Linux, which jumped more than 16% in June — albeit from a small base — to hit 0.79%.

The iPhone held steady at 0.16%, reflecting a leveling off of what had been double-digit growth as buyers waited for the new iPhone 3G, which goes on sale next week. In a separate survey issued Monday, RBC Capital reported “unprecedented pent-up demand” for the new model. Data taken from 3,600 members in RBC’s Technology Adoption Panel in early June showed that 56% of those planning to buy a smartphone in the next 90 days planned to buy an iPhone — up from 35% in March and more than double the interest in any of the other brands surveyed. See here for more detail.

The monthly Net Applications survey is conducted by sampling browser data from some 160 million visits to websites operated by the firm’s clients. Although it describes the results as “market share,” Net Applications does not actually measure share of market in the traditional sense by revenue or unit sales. It does, however, provide a consistent methodology by which to measure operating system trends.

To see their July 1 report, click here. The results are summarized in the table below.

Drilling deeper into the numbers, ArsTechnica’s Charles Jade notes that the numbers for Intel Macs grew by a quarter of a percent to 5.26 percent, while PPC Mac’s declined to 2.7 percent. In other words, Intel Macs increased at twice the pace of decline for PPCs. “The rapid decline of PPC Macs coupled with sharp gains for Intel Macs no doubt factored into the decision to make Snow Leopard Intel only,” Jade speculates. His chart below:

UPDATE: Net Applications’ model must be more dynamic than we knew. At sunrise in New York on Monday, Mac’s June share was 7.95%. By 8:30 a.m. CT, when Jade posted his report, it had risen to 7.96%. By 3:00 a.m. ET Tuesday it had dropped to 7.94%. And these are last month’s numbers!

Apple’s mail service was offline for about five and a half hours Monday night, and a lot of people got very excited.

“.Mac mail down, speculations abound” read the headline on The Unofficial Apple Weblog (TUAW).

“.Mac outage sparks fresh re-brand rumour” echoed 9to5Mac.

Why the excitement? Because everybody who follows Apple believes that an overhaul of the company’s aging Internet services bundle is imminent. And indeed, one regular at Investor Village reported later that night that a “buddy at Apple” told him that the outage was related to “major server work” and not the irritatingly regular scheduled maintenance.

It’s been more than a year since Steve Jobs, gently rebuked at D5 by the Wall Street Journal’s Walt Mossberg for how little Apple (AAPL) has done to develop its $99/year .Mac Internet bundle — especially compared with what Google (GOOG), Yahoo (YHOO) and Microsoft (MSFT) now offer for free — promised to do something about it real soon.

“I couldn’t agree with you more,” Jobs replied at the time. “And I think we’ll make up for lost time in the near future.”

A few months later, Apple did increase tenfold (to 10 GB) the amount of storage you get for $99, but the rest of the .Mac services — Mail, Backup, Sync, iDisk, etc. — were basically unchanged and growing increasingly long in the tooth.

So with less than a week left before Apple’s annual World Wide Developers Conference and the keynote speech at which everybody expects Jobs to unveil the new iPhone, at least one Apple watcher thinks his surprise “one more thing” this year might be the successor to .Mac, re-branded for the age of iPhones as .Me.

Why .Me? Saul Hansel at the New York Times’ Bits blog does a good job tracing the genealogy of this particular meme, from .Mac to %@ to Mobile Me to .Me.

Suffice it to say that this may be Apple’s best chance to prove that it really does understand today’s World Wide Web, and that it can do for social networking, cloud computing and online services what it has done in the past for PCs, portable music players and cell phones: put the focus on the user’s experience and make complex technology seem utterly and delightfully transparent.