The Natural Resources Defense Council has an action page where you can learn about the effects of global warming on polar bears and then personalize and send a letter to the Bush Administration requesting action to slow global warming and list the polar bear as a threatened and endangered species.
Although Arctic animals may be experiencing the most dramatic climate change impacts to their habitats, animals in your neighborhood could also benefit from some habitat help. The National Wildlife Federation has a Backyard Wildlife Habitat program where you can learn how to create homes for songbirds, butterflies, frogs and other wildlife while reducing the use of chemicals, conserving water and energy, and helping to improve air, water and soil quality.
Reducing and offsetting your own carbon emissions can also help slow global warming and help protect ecosystems. Environmental Defense helps you calculate your carbon footprint and then figure out ways to reduce it.