Visit the Earth Day 2011 site to tap in to a variety of activities to mark the observance of Earth Day this year. Find local events and campaigns to take part in via the Take Action section. This year’s Earth Day focuses on A Billion Acts of Green - personal, organizational, and corporate pledges to live and act sustainability. Read about the campaign and submit a pledge. From the simple to the complex, it’s the largest environmental service campaign in the world, featuring: 1) Athletes for Earth: Olympians championing environmental efforts; 2) Canopy Project: global reforestation; 3) Green Schools: greening schools within a generation; 4) Women and Green Economy (WAGE); 5) Creating Climate Wealth - entrepreneurs tackle climate change and green economy; 6) Arts for the Earth: celebrating environmental artists. You can also use the Earth Day Network Footprint Calculator to measure your impact on the planet. Tie digital library resources to Earth Day activities by using NSDL resources from a variety of contributors: from the Applied Math and Science Education Repository (AMSER):  The Wilderness Society (TWS) website for Earth Day, with historical and biological information, sections for teachers and kids, bird migration, American wilderness, and suggestions for getting involved;  Geologic Time: the Story of a Changing Earth, from the Smithsonian National Museum of Natural History is an interactive timeline of geological history. Explore the collections of exemplary resources on a variety of climate and earth science topics from the Climate Literacy and Energy Awareness Network project, Teacher’s Domain, and the Middle School Portal.  Use the Earth Science Literacy Maps from the Digital Library for Earth System Education (DLESE), to discover more resources. From NSDL’s Engineering Pathway, read up on the first Earth Day, April 22, 1970, from EP’s Today in History blog; browse through Images of Earth Day World-Wide; and just for fun, explore Earth Day Pictures: Quirky Ways to Mark the Day.