Although Alleys of Seattle was last updated in October, the blog is a great resource for alley fans. The blog's author, Daniel Toole, was interviewed by The Atlantic Cities in February 2012. Tight Urbanism, Toole's book about alleyways in the U.S., Australia, and Japan, was published last year.
Earlier this year I came across Alleys: A Hidden Resource (1978) written by Grady Clay. He also authored Close Up: How to Read the American City (1980) and developed the field method of walking a transect as a way of "reading" a place.
On this blog, I profiled the mews of New York's Greenwich Village.
Finally, Joshua P. Newell et al. (2012) compared alley greening programs in several U.S. cities and found that most are focused on stormwater management. The program in Los Angeles was singled out as an example of "a more robust commitment to sustainability" because it was designed to achieve multiple benefits ("environmental protection, economic development, and social equity"). The article, "Green Alley Programs: Planning for a sustainable urban infrastructure?", in press at Cities is available here.