This is your one-stop place for accessing information on programs and services offered through the City of New York: ACCESS NYC
Here's the NYC Department of Education SchoolFood and NYS Child Nutrition Knowledge Center - tons of links for grants that schools can apply to, etc etc.
Here are some resources on reducing obesity and diabetes in NYC that I learned about at a conference at the CUNY Graduate Center:
Publications by the Public Health Association of NYC
Of particular interest are these few:
Reversing Obesity in NYC - includes some great statistics on obesity and fast food, and advocacy strategies (and here's a shortened version)
Reversing the Diabetes and Obesity Epidemics in NYC
Here are resources from the District Public Health Offices. There are DPHO's for East & Central Harlem; North & Central Brooklyn; and the South Bronx. They have regular meetings that anyone can attend, if you are interested in voicing your opinions. You can check out the NYC Food and Fitness Partnership website and sign up for their mailing list here.
Also, here's a blog on healthy things going on in NY from New York Cares - http://blog.nycares.org/