Science - NASA for middle-school students http://www.nasa.gov/audience/forstudents/5-8/features/index.html
Science - Volcanoes of the World http://www.volcano.si.edu/world/allvolcs.htm
Science - Volcano World http://www.volcano.und.nodak.edu/vw.html
Math - From the back of the envelope - interesting facts http://www.vendian.org/envelope
Math - Purple Math - Pre-Algebra / Algebra resources http://www.purplemath.com
Math - Algebra Solutions - step by step help with Pre-Algebra / Algebra concepts http://www.gomath.com
Science - current information on earthquakes / detailed information - even a place to log in and report if you felt an earthquake. Browse science topics under Hazards for earthquakes and more. A wealth of science info in many science related areas. http://www.usgs.gov