The Biology Corner is a fantastic web site my wife found this weekend. The site has resources for teachers including lesson plans, web quests, quizzes, and much more. The site is set up by "class" - Anatomy 1 and 2, AP Biology, Biology 1 and 1a, Biology 2 and 2a, and Physics.
Worksheets are also sorted by topic, and images and media have their own menu.
The material is very useful and I like the class format for the resources. It is set up sequentially and allows for easy scanning for resources.