The following links are just a few I have found useful.  I will continue to add more as I become aware of them.  I try to avoid sites which advertise but will follow links to useful sites and add them here if they seem appropriate.

Biology

Chemistry

Physics

Geology

Multi - dicipline

Nasonia

Periodic Table

  

 Academic Pages for High School

 Biodidac

bank of digital resources for teaching biology

Web Elements

  

EduGate

 On-Line Biology Book

 Periodic Videos

Videos based on the elements and other chemical topics

  

 National Science Teachers Association

 Online Schools

Biology

   

National Science Foundation Classroom

 Group Names

   

SCOPE

Scientific Committee on Problems of the Environment

Coat Colors of Mice

   

The Company of Biologists

 Macroinvertebrate Pictorial Key

   

Virtual Library

 Poisonous Plant Database

   

National Geographic

 The Insects

   

 Teach-nology

Insects as Food

   

IRIS

Integrated Risk Information System

Tree of Life

   

 Helio viewer

A sight with a downloadable viewer to look at images of the sun

National Association of Biology Teachers