A few months back I wrote
about the "public space" zoning regulations. There's now been a new article
about it. I don't think there's much new information there that wasn't covered in the links you folks posted in the comments, but there is a pretty slick Google Maps display
of all the spaces mentioned in the article.
Oh, and that one on 2nd Street that I made fun of? "Enclosed empty concrete lobby as public park"? The article says, "Though passers-by must pass through doors to use the chairs and black granite benches, the space feels like an urban piazza."
Suuuure it does.