By Tim ChanMainStreet is on a mission to find the charitable organizations most worthy of your donations. We focus on their effectiveness and the amount of money they budget for actual good deeds, as opposed to that which goes to overhead. Donating enables you to do good and cut your tax bill. This week we're looking at The Nature Conservancy. President Obama's American Reinvestment and Recovery Act promises up to $19 billion for clean water, flood and environmental restoration projects in the U.S. But when it comes to protecting the environment, the federal government can't do it alone, and there's the rest of the world to think about, too. That's where this Arlington, Va.-based organization comes in. Who they are and what they do: The Nature Conservancy is one of the largest environmental nonprofits in America. In the 58 years since its founding, the conservancy has been able to save more than 119 million acres of land and 33 million acres of marine areas in places as varied as Montana and Micronesia through outright acquisition. "Our strength lies in big projects, such as our $1 billion Montana Legacy Project and a $210 million acquisition of land in the Adirondacks," says Bill Ginn, the chief operating officer. Billion-dollar real estate deals may seem out of place in the current economic climate and even unusual for a non-profit. However, using the organization's $1 billion endowment as equity, the conservancy is able to save wildlife and protect biodiversity in more than 30 countries, support scientific research in the field of climate research and empower indigenous people throughout the world to advocate for the responsible use of natural resources.