I love garden 'before and after' photos. They can be just as fun for me as apartment redesign photos. The Horticulture Society of New York, a non-profit that is over a century old, is responsibe for creating (and maintaining) gardens in a number of public libraries in NY's boroughs.
They also have a fantastic blog written by their Director of Horticulture, Alex Feleppa.

Check a few before/after pics from their site after the jump...
Flatbush branch before
Flatbush branch after
Dekalb branch before
Dekalb branch after
To see the other branches the society has helped take a look at photos of their projects here.
The society is also a great resource for anyone in the city who needs help with plant or garden questions.
The blog is, seriously, great. Alex Feleppa is a recent grad of the NYBG Hortculture program - his posts are thorough and you can tell he's excited about what he does. The blog, which is all about plants in the NYC area, is a resourceful archive of his daily travels, HSNY events, and questions posed to the HSNY about plants. Thanks Alex!
matt at apartment therapy dot com