Officially, Carnegie says the 542 grants are the latest in a string of gifts by an anonymous donor who has given more than $175 million over a period of seven years to New York's nonprofit community - but it's widely known that the donor is Bloomberg.
The beneficiaries include well-known names like the Alvin Ailey Dance Foundation, Apollo Theater and Brooklyn Botanic Garden, but also smaller performance spaces in Brooklyn, Staten Island and the Bronx.
The social service organizations range from Big Brothers/Big Sisters of New York, Citymeals-on-Wheels and the Gay Men's Health Crisis to numerous community centers and programs for job training and the homeless.
The Carnegie Corporation said it has been selecting small and medium-size New York City-based organizations to receive the donor's funds since 2002.
Bloomberg, a billionaire many times over after founding his financial information company, was ranked No. 7 on The Chronicle of Philanthropy's 2007 list of the country's Top 50 donors.
The two-term mayor has said he plans to focus full time on philanthropy once he leaves City Hall at the end of 2009. To that end, he established the Bloomberg Family Foundation.