Mayor Bloomberg is calling for more volunteers around the city to help clean up neighborhood blocks and teach free fitness classes to prevent obesity. The call for public service is part of the mayor's 'Give Your BLANK' campaign. It's based on the idea that everyone has something to give, whether it's time, skills or passion.

What's Bloomberg's blank?

'My blank is the ability to work with people, trying to help people, encourage them, believe that anything's possible, and I suppose another blank -- making money and giving it away,' the mayor said.

One of the campaign's initiatives will expand the number of free fitness classes in parks and community centers across the city. The city will recruit 100 new volunteer fitness instructors to teach yoga, Pilates, dance, and martial arts.