Huge set of free math games covering math topics for students of almost all grade levels. Topics:
Sheppard Software has hundreds of free, online, educational games for kids. They cover many subjects including geography, math, animals, and science, with games and activities for learners of any age.
Sheppard Software geography lessons for the US states and various countries around the world are particularly popular, but Sheppard Software Math, Sheppard Software Brain Games, and Sheppard Software Science are also great places to start.