Sales of existing homes, which had been in the doldrums for quite a while, have picked back up briskly, says the latest report. According to the National Association of Realtors, sales spiked 7.2 percent in July, to an annualized total of 5.24 million, the fourth monthly increase this year. In the ten years that the association has been tracking existing home sales, there has never been a larger monthly increase.