Extraterrestrial Life « Astronomy

See also:

This category in other languages:

The Planetary Society - A nonprofit organization devoted to the exploration of the solar system and the search for extraterrestrial life.
The Rise and Fall of Star Faring Civilizations in Our Own Galaxy - Speculation, based on the Drake Equation, regarding the existence and composition of alien civilizations.
Search for ET! - Interactive Flash tutorial exploring the possibility of and search for life on other worlds.