Lesson Plan Sites and General Science Sources
The Why Files - "The Why Files produces a new story each week, alternating longer features with shorter shorties. We also post a series of interactive science animations, the ever-popular “Cool Science Images,” and a series of Teacher Activity Pages linked to the national science teaching standards. Eager to explain the science behind the news, our home page reprises older stories that become relevant to the headlines."
Edumedia - Interactive simulations and animations for Science teaching and learning
NOVA Science Now from PBS
HippoCampus - online textbook and tutorials on science topics including biology and physics (geared to High School)
U.S Geological Survey - "As the Nation's largest water, earth, and biological science and civilian mapping agency, the U.S. Geological Survey (USGS) collects, monitors, analyzes, and provides scientific understanding about natural resource conditions, issues, and problems. "
Science Gems - " More than 14,000 Science Resources sorted by Category, Subcategory, and Grade Level"
National Geographic for Kids
ScienceBuddies - Science Fair answers, ideas, and tools
Science Up Close - Simulations from HMH School Publishers
Discover Simulations - grades K-5 from HMH School Publishers
American Museum of Natural History - interactive activities for many topics of Science study
I Was Wondering - Women's Adventures in Science from the National Academy of Sciences
LearningScience.org - " dedicated to sharing the newer and emerging "learning tools" of science education. Tools such as real-time data collection, simulations, inquiry based lessons, interactive web lessons, micro-worlds, and imaging,  among others, can help make teaching science an exciting and engaging endeavor."
Educational games and activities "Edheads helps students learn through educational games and activities designed to meet state and national standards. We partner with various school systems in the United States, which help us research, design and test our activities every step of the way!"
How Stuff Works
National Science Digital Library - "Explore, share, learn, and create"
The Exploratorium – the museum of science, art, and human perception
National Science Foundation - "Classroom Resources--a diverse collection of lessons and web resources for classroom teachers, their students, and students' families. Materials are arranged by subject area to help you quickly find resources in your interest area, and then use them to create lesson plans or at-home activities."
NASA Climate Time Machine - Tracking global conditions over time
Stop Disasters Game
Who Can Resist? - a game about circuits


Biology
BioMed Central - Archive of over 170 biology, chemistry and medical journals, peer-reviewed to ensure accuracy and appropriateness for research, some articles require subscription service to access
Cells Alive
National Science Foundation – tour of the cell
Critter Cam
National Geographic Creature Features
ArkLive - a unique collection of thousands of videos, images and fact-files illustrating the world's species.
Brains Rule – Kids link to interactive games that teach about the brain
The Shedd Aquarium – Interactive Lessons
MedMyst - solving medical mysteries on the web
Genetics Web Lab
Plants – the science of gardening
The Knowing Trail - The Rainforest
The Great Plant Escape - third grade science
Insects on the Web - Bug Bios
Cool Science for Curious Kids
Bite Size Biology
Inner Body Online
NobelPrize.org - educational games/medicine

The Environment
Global Warming Facts and Our Future
Human Footprint from National Geographic
Safe Drinking Water
Glossopedia - Tropical Rain Forest
Discover EarthLive - The state of the planet, covering many topics relating to the environment


Physics
Physics Central
Building Big
Amusement Park Physics
Skate Park Simulation (check out the rest of the simulations from the home page too!)
PowerPlay Simulation
Flash Animations to illustrate Physics concepts
Fear of Physics - "a friendly, non-technical place for you to come and "play" with the laws of physics for a while. Hopefully you'll find that Physics explains a lot about the world around us, and that it's really not that bad!"
Simple Machines Game - from the Museum of Science and Industry
Fantastic Contraption - watch out for the ads
Phun - 2D Physics sandbox, this is the link to the wiki that goes along with the program

Solar System
Solar System Exploration
Windows to the Universe
The Moon Wiki