Nice NY Times piece about ADUs (November 11th, 2011)
There's a 5 minute audio piece as well. It's about an ADU in Raleigh, NC.
This paragraph was particularly enlightening to me: "According to the American Planning Association, at least four states California, Massachusetts, Vermont and Washington have enacted laws encouraging or requiring changes to the zoning rules to permit the so-called accessory dwelling units, also called A.D.U.'s. Architects said that parts of Oregon, Colorado, Texas and Virginia had also become more accommodating. And last year in New York, then-Gov. David Paterson signed a law that will ultimately develop model planning and zoning guidelines for communities to create senior housing and granny flat accommodations. "