Best-selling “Freakonomics” co-author Stephen J. Dubner strikes a multimedia deal with American Public Media and WNYC parent New York Public Radio to offer radio, podcast, web and live-event programming. That includes features for APM’s popular “Marketplace” syndicated show. Plans are also in the works for five hour-long radio specials. Dubner says “I've loved radio since I was a kid, and I particularly love public radio for its smarts and reach.” Dubner and his colleague Steven Levitt will keep preparing the daily Freakonomics blog for the New York Times online, and Levitt will drop in on the new radio podcast from time to time.