In the latest suggestion of an advertising slowdown, MediaPost reports that the eyeball-and-bean counters at Nielsen say “that for the first half of 2007, ad spending slipped 0.5% versus the same time period for 2006.”

Nielsen findings (press release) corroborate other ad-tracking sources in suggesting that ad spending has softened after a strong run.

In his summary MediaPost reporter Wayne Friedman notes that most print categories were down mid single digits; broadcast ad dollars also retreated but less markedly; outdoor advertising showed continued strength; and, he wrote, the “Internet led the way–again–as the most improved category, up 23.6% versus a year ago. ”