Effects of El Niño on Streamflow, Lake Level, and Landslide Potential
A thorough overview of the topics contained in the title. Also has a nice "What is El Niño?" section.

El Niño and California Precipitation
This site discusses the current event and its possibilities for California precipitation. Updated regularly with many images and charts.

El Niño and the National Landslide Hazard Outlook for 1997-1998
This USGS site provides maps showing the possible landslide hazard based on expected precipitation this winter and spring.

El Niño Rules
This excellent resource from the "Why Files" will tell you just about everything you'd every want to know in a very readable format. Includes history, causes, effects, El Niño's possible relationship to global warming, and more.

El Niño Theme Page: Accessing Distributed Information Related to El Niño
The NOAA (National Oceanic and Atmospheric Administration) comprehensive El Niño site. Includes current information, forecasts, data, and much more.

El Niño/Southern Oscillation (ENSO) Information
The NOAA Climate Diagnostics Center's site includes the latest advisory, a "What happens during an El Niño?" section, and much more.

FEMA El Niño Loss Reduction Center
The Federal Emergency Management Agency's resource for preparing for El Niño.

NOAA La Niña Page
A comprehensive La Niña resource.

Nova Online: Tracking El Niño
Lots of information about El Niño from NOVA; includes in-depth features about its history and current status.

Special Climate and Weather Summary
The NOAA special report outlines the effects of El Niño, especially rainfall and temperature changes across the U.S.