Galileo's Sharp New pictures of Io Detail Amazing Volcanism: Press release from the University of Arizona.
Io During 1999: Volcanic activity on Io during 1999 as seen from Earth.
Io: Jupiter's Volcanic Moon: Discussion of many geographic and geologic features of Io. Includes links, photo glossary, and a test.
Ionian Web: Provides information, images, maps, scientific articles, links, and the latest news concerning Jupiter's volcanic moon.
Jupiter's Volcanic Moon Io: Strange Shapes in a Sizzling World: Press release concerning near-infrared images taken by Galileo during its 27th orbit.
PIRL: Galileo Images of Io: Many pictures from the Galileo Mission, taken between August 1999 and December 2001.
Scientists Show Jovian Moon Io's Mantle is Similar to Earth: Press release from Washington University in St. Louis.
SO2 Ice on Io: A short scientific article about the identification of Sulfur Dioxide ice on the satellite's surface.
Solarviews.com: Io: Statistics, animations and annotated pictures.
The Nine Planets: Io: Overview with data, text, images, links.