An unnamed search engine has reported traffic from a product purporting to be Apple-made but with a screen-size larger than that of the iPhone but smaller than that of MacBooks. The disclosure was made to John Markoff of the NYT, on the understanding that their identity be protected, and instantly the speculation began that Apple is testing its own netbook or tablet.
In the recent Apple financial earnings call, Steve Jobs made a surprise appearance to discuss the company's performance and answer some questions from press and analysts. Quizzed about the possibility of a low-cost Apple device, he told those listening that "We don’t know how to build a sub-$500 computer that is not a piece of junk"; however he also reiterated the company's wait-and-see stance on netbooks.
Of course, without full details of what was spotted on the search engine server logs it's difficult to do anything other than speculate. The mysterious visitors could be a new, in-development Apple product or it could be a netbook hacked to run OS X - such as this Gigabyte M912X or this MSI Wind - and browsing using Safari on a smaller display. The likelihood of each depends on where the visits came from (inside Cupertino would make the former mildly more likely, perhaps) and what other facts are known.