Math

Babylonian Math

Math Cats

Cyberchase

Mancala

Timez Attack

A great (free) game for memorizing multiplication facts

Multiflyer

Math Homework Help

Ask Dr. Math

6th, 7th and 8th grade math textbooks

Algebra vs. the Cockroaches

Science

Beakman's World Experiments

Bill Nye the Science Guy

Amusement Park Physics

Smithsonian Education

Track Satellites Orbiting Earth!

Click on J-Track 3D

Geography

National Geographic Kids

GeoSpy

Computers

Squeakland

Robots

Design Your Own Robot

Robot Constructor

RoboCup