Casey Trees - A nonprofit with a mission to restore, enhance and protect the tree canopy of the nation's capital. District Department of the Environment - Promotes energy efficiency through conservation, education, and fuel assistance programs and by regulatory intervention. Includes consumer information, a description of agency programs, a guide to resources in its library, an events calendar, and links to related sites. HowStuffWorks: Exploding Manholes - Information on the frequent mishaps under the streets of the city. Biodiversity Database of the Washington, D.C., Area - Searchable database of information and images. Includes organisms and regional nature and preservation areas in the D.C. area. Pre-Columbian Society of Washington, DC - Promotes interest in Pre-Columbian cultures through annual symposia, monthly meetings, and a newsletter. Includes newsletter index. Flora of the Washington-Baltimore Area - Offers information about flora native to the area. Includes a specimen database, projects, spring flowering records and a gallery. Audubon Naturalist Society - Independent conservation organization serving the Washington D.C. metropolitan region. Find programs, classes, current issues, news, and information about sanctuaries in Maryland and Virginia. DC Nature - Photo galleries of DC area wildlife created by a local group of nature photographers. D.C. Science Writers Association - An organization of science writers and editors from nearly all the major news outlets in the Washington area that meets monthly for tours, symposia, and professional development. DC Department of Health - Environmental Health Administration - Works to prevent and control environmentally related diseases while protecting and preserving the ecological system in the district. Features a guide to the bureaus and divisions that make up the Administration. Bushmeat Crisis Task Force - Headquarters for consortium of conservation organizations and scientists dedicated to the conservation of wildlife populations threatened by commercial hunting of wildlife for sale as meat. Sierra Club: Washington, DC Chapter - News and issue information from the local chapter of the environmental organization. Urban Land Institute - Non-profit research and education organization focusing on the use of land to enhance the environment. National Capital Area Skeptics - Group promoting critical thinking and scientific understanding. Includes information about events, newsletters, and a document library. Friends of the Earth DC Environmental Network - A consortium of conservation organizations that meets regularly to focus on environmental problems specific to the region, exchange information, and coordinate strategies. Includes background documents [PDF]. Maryland-National Capital Park and Planning Commission - Acquires, develops, maintains and administers a regional system of parks in Montgomery and Prince George's Counties in Maryland. Audubon Society of the District of Columbia - Field trips, events, birding around D.C., Logan Meadow sanctuary and newsletter articles. The Nature Conservancy - Maryland/District of Columbia - Works to protect critical natural lands. Features places protected, events, news and volunteer opportunities.