"Seinfeld" and "Sex and the City" have their own New York tours, so why not "Mad Men"? Gridskipper -- the excellent, insidery international travel blog edited for Gawker Media by Chris Mohney -- just launched a Google Maps mash-up called "The 'Mad Men' Guide to New York."
It maps and pithily summarizes locations that are key to AMC's historical ad-industry drama, including both real (e.g., P.J. Clarke's, where Peggy Olson celebrates getting her ad copy accepted) and notional spots (like Menken's Department Store, which Gridskipper places at the pre-1990 Henri Bendel HQ at 10 West 57th, in part because "the slight parallels between Rachel and Bendel's groundbreaking female exec Geraldine Stutz are pleasing enough to make the connection"). Mohney tells me he'll update the guide as more actual New York locations pop up in the show and "as I get reader tips with theories about other obscure locations."