Learn Genetics and Teach Genetics are great resources from the University of Utah.
Learn Genetics has interactive videos and demos that explain different concepts of genetics. The web site is nicely designed and easy to navigate.
Teach Genetics is a beta preview teacher companion site for Learn Genetics. There are some resources now, with more coming in the future.
These are great resources for Biology and Genetics teachers.
My wife, a Biology teacher, found them and told me about them. She found them very useful and easy to use.