National Centers for Environmental Information (National Oceanic and Atmospheric Administration): "NOAA's National Centers for Environmental Information (NCEI) is responsible for preserving, monitoring, assessing, and providing public access to the Nation's treasure of climate and historical weather data and information."
USGS (United Stated Geological Survey): "We provide science about the natural hazards that threaten lives and livelihoods, the water, energy, minerals, and other natural resources we rely on, the health of our ecosystems and environment, and the impacts of climate and land-use change. Our scientists develop new methods and tools to enable timely, relevant, and useful information about the Earth and its processes."
USGS Geologic Hazards Science Center: Provides overviews of geologic hazards--such as earthquakes and landslides--as well as more detailed data.
Geologic Hazards (National Park Service): Provides general information, including additional resources, for a number of geologic hazards including landslides, sinkholes, tsunamis, avalanches, hurricanes, and floods.
Global Climate Change: Vital Signs of the Planet (NASA): This website, provided by NASA, contains a wealth of information in an easily understood format. There are articles, facts, and data available to read.
Climate Change (Environmental Protection Agency-EPA): This website by the U.S. EPA provides a number of articles written in a very digestible format. There is even a section to look at how climate change influences the climate in your state.
Grand Canyon Geology Training Manual: While this manual is aimed at the geology of the Grand Canyon, you can download the glossary from this page. The glossary contains a wealth of geological terminology.