This site has lesson plans and activities related to radiation. Activities include measuring radiation with a Geiger counter and observing radiation 'footprints' in a cloud chamber.

Explains how radiation is produced and the characteristics of alpha, beta, and gamma radiation.

This article with embedded videos provides information about three main types of radioactive decay: alpha, beta, and gamma.

Explains what is meant by the half-life of a radioactive element and how it is calculated.