Reliefweb provides maps of recent and current natural catastrophes where relief efforts are currently being undertaken.
This site provides access to online images of historical maps throughout history.
Intellicast provides interactive maps of current weather conditions and weather forecasts throughout the world.
This site offers access to L-THIA - Long term Hydrologic Impact Assessment. The site, which is sponsored by Purdue University, allows users to model alterations in a development area to estimate the impact on runoff and pollution. The site has coverage for all of the watersheds in the United States.
The IPCC, which has been in existence for twenty years, provides information on climate change issues including speeches, presentations, power point slides and publications, many of which are available here at their web portal online.
This is the United Nations agency for meteorology, operations hydrology and related geophysical services.