NOAA
Noaa: Pmel: El Nino Theme Page
The National Oceanic and Atmospheric Administration (NOAA) sponsors this El Nino and La Nina resource site that features current and historic information about these weather systems with diagrams.
NASA
Nasa Earth Observatory: The Color of El Nino
This article explains the effects El Nino has had on different climates and natural disasters throughout the world.
PBS
Nova: Into Living Things
Paleoclimatologists use information from tree rings, corals and ice cores to learn more about El Nino. See if you can analyze samples of each of these types of evidence to look for past El Nino events.