DNA is a great resource from PBS. The site has resources on DNA separated into episodes. Life, Playing God, Human Race, Curing Cancer, and Pandora's Box are the 5 episodes. Each "episode" is a web page with information about DNA and how it applies to different topics. There are links to more in depth resources, videos, and much more. There is also a timeline of DNA research and discoveries and a 3D DNA Explorer (uses Adobe Shockwave) that allows you to manipulate a 3D image of a DNA segment. You can rotate and zoom in on different parts of the segment.
DNA is a great tool for biology teachers as it gives them and their students scientific information as well as touching on issues relating to society and ethics.