More than 500 organizations across the city are receiving cash infusions, thanks to an “anonymous donor” a source says is none other than Mayor Bloomberg.

The $30 million donation to the Carnegie Corporation marks the seventh consecutive year that Mr. Bloomberg has entrusted the organization with sprinkling his money to arts, cultural, public health, and religious groups throughout the city.

Among the 530 groups slated to receive $10,000 to $150,000 grants are: Agudath Israel of America, the Gay Men’s Health Crisis, the Brooklyn Academy of Music, and Jazz at Lincoln Center. A vice president at the Carnegie Corporation, Susan King, said letters went out yesterday to notify the organizations receiving grants.

A spokesman for Mr. Bloomberg, Stuart Loeser, declined to comment, but a person familiar with the donation confirmed that the mayor and his checkbook were behind it.

Mr. Bloomberg’s “anonymous” donations through the Carnegie Corporation now exceed $115 million since 2002. The donations have sharply increased over the last few years. He gave $10 million in 2002 and 2003, $15 million in 2004, $20 million in 2005, and $30 million last year and again this year.

He has also made a point of giving to a wide variety of organizations in all five boroughs, which has allowed him to build relationships and allies.

This year’s gift comes as Mr. Bloomberg, a multibillionaire, is signaling that he is gearing up to run for president even as he claims that he going to be a full-time philanthropist when he is term-limited out of City Hall.

The donations given through Carnegie are just a portion of Mr. Bloomberg’s overall charitable giving. In February, the Chronicle of Philanthropy ranked him the 10th most generous philanthropist in America for 2006; he gave away $165 million of his personal fortune in 2005. He has also given $125 million for worldwide anti-tobacco programs.