Market research firm NPD Group has published a report that finds there are now more than 500 million devices in US homes that connect to the Internet. And for the first time, smartphones and tablets outnumber PCs in that tally.

NPD's Connected Intelligence report found that households now have an average of 5.7 devices (up from 5.3 just 3 months ago). That mushrooming cloud of bandwidth-demanding devices has been driven by the red-hot tablet market—there are now tablet devices in 53 percent of homes in the US, up from 35 percent in December. Smartphones also have edged into 9 million more pockets over the last three months, according to NPD, and they now account for 57 percent of cell phones in the US market.

Calling it the "post-PC" era may be a little premature. Despite the explosive growth of mobile devices, PCs still remain the main way that people connect to the Internet. NPD reports that PCs are present in 93 percent of US households—a slight, statistically insignificant dip from December. But as NPD's Director of Connected Intelligence John Buffone said, "When you look at the combined number of smartphones and tablets consumers own, for the first time ever it exceeded the installed base of computers."