Learners.tv - free science videos for difficult concepts and animation at Science animations on Learners TV are organized into three categories; biology, physics, and chemistry.

Science News For Kids - A collection of the latest news written for kids that will fit into any project.

Science Journal for Kids and Teens Free reports on cutting-edge, peer-reviewed science research adapted for students and their teachers. Articles can be selected according to reading level (elementary school, lower high school, middle school, upper high school) and/or subject field (biodiversity and conservation, biology, energy and climate, food and agriculture, health and medicine, physical science, pollution, social science, technology, water resources).

Medmotion - learning celular and body systems interactively

NEOK12 -  videos about Maths, Eng, Science and HSIE

Explania animated explanations of topics in technology and science. Some of their offerings are videos and some of their offerings are interactive animations. One of their interactive animations that could be quite useful for biology teachers and health teachers is The Human Heart.

Frontiers Science For Kids - Not only are these articles for kids... they are written by kids. Perhaps your students could be the next contributor.

Interactive Science Animations for Children animated lessons covering seven science subjects for students of early elementary/ primary school age. The lessons cover The Body and Medicine, Energy and Environment, Earth and Beyond, Teeth and Eating, Micro-organisms, The Brain, and Exercise.For each science subject covered there is an introduction followed by seven to ten interactive animations. For example, in The Earth and Beyond students can see how the position of the sun affects the length of shadows. Students can advance the sun through the sky. As they advance the sun they can use a ruler to measure the lengths of the shadows that they create.

Open Culture has curated a list of 125 science videos. Their list is divided into subcategories. Each video has a brief description and a link to the video with a more detailed description.

Nuskool This is a site that uses pop culture as teaching moments for students.  Tailored to grades 6th-12th students learn a variety of subjects such as: Math, Science, English, etc through educational lessons based on the different elements of pop culture (video games, sports, films, etc.).

Gooru is a search engine for learning that allows you to explore and study over 2,600 standards-aligned and personalized study guides. Study guides cover 5th-12th grade math and science topics, and resources include digital textbooks, animations, instructor videos and more. All resources are vetted and organized by teachers or Gooru’s content experts, so you don’t have to sort through the mess of subpar educational resources available online yourself.

Science animations on Learners TV are organized into three categories; biology, physics, and chemistry.

American Field Guide - Over 1400 short video covering all areas of science.

Exploratorium TV - Browse hundreds of webcasts, video clips, podcasts, and slideshows from the Exploratorium's collection of original programming, from remote scientific expeditions to fun hands-on activities.

Sports Science - Awesome collection of short videos that will engage kids in science and math from the people at ESPN.

Seven Wonders of the Microbe World. The Seven Wonders of the Microbe World is a seven part series of short videos exploring things like the Black Death, antibiotics, and food preservation. You can watch the videos individually or watch them as one combined 25 minute long video.

WISE - create an interactive web based science inquiry environment.

PBS Learning Media has a free service called Learning Media.  Resources include pictures, video and interactive materials from a robust library of high-quality digital content from PBS, and a growing list of other contributors including the National Archives, Library of Congress and NPR. There are research-based resources, including videos, interactives, images, audio files and lesson plans. You can view three resources.  Then you have to create an account which is free. Can be filtered by grade level (Pre-K to 12+), subject (8), media type (document, audio, video, etc.), language (5) and accessibility (text, audio description, display transformation, etc).

National Geographic Young Explorer Magazine Online - (gr 1-2) read text or use audio option

Science Behind the News.  In partnership with the National Science Foundation, NBC explores the science, technology and engineering found in current events.  Here, you will find a collection of videos that introduce students to the science found in the world around them and current events.

Science Games FunSchool  K-3

Lesson searchable by grade and subject. Often include videos http://uw.kqed.org/edresources/ 

How Stuff Works Science - Excellent collection of videos that cover interesting and engaging topics across the science curriculum.

The Science of Cooking (gr 9-12)

Gooru is a service that aims to provide teachers and students with an extensive collection of videos, interactive displays, documents, diagrams, and quizzes for learning about topics in math and science. Access to hundreds of resources according to subject areas such as chemistry, biology, ecology, algebra, calculus, and more. Within each subject area you can look for resources according to media type such as video, interactive display, slides, text, and lesson plans.  

Understanding Science - a resource for teachers and students - explains science in a way that is easy to understand.

The Why Files (gr. 4-8) is a resource designed for students to learn about the science of stories in the news. The teachers' section of The Why Files offers pdf guides and quizzes that you can use to teach the science of the stories featured on the front page of The Why Files.

Planet Science Interactive science website features eight specific areas. The "News" section includes weekly news updates and features. Natural World, Human Body, Space, Chemistry, Physics There are printable pages and interactive activities for elementary, middle, and high school students. The "Library" link features countless online science resources.

Science Magazine's Video Portal offers dozens of videos across a variety of topics in science. Each of the videos is connected to an article that you can read online or print for classroom distribution. The Science Interactives menu contains six interactive versions of posters they have published in recent years.

Science NetLinks is a place to find quality science and engineering resources for the classroom, including lesson plans, interactives and podcasts. 

Hey LHS Kids (gr. K-6) is a science activities website for kids developed by the Lawrence Hall of Science at UC Berkeley. Hey LHS Kids features some good activities for elementary school students. One of the activities on the site that I think would be fun for elementary use is Measure Yourself. Measure Yourself asks students to measure the size of their ears, feet, and overall height in centimeters. Students then plug those numbers into Measure Yourself and are shown a list of animals that have similar dimensions.

Water Cycle Animation

Weather Basics This page consists of links to USATODAY.com graphics and photo scrapbooks with captions explaining the photos. These resources will help you understand weather, climate, and some other earth science topics. Most of the links are to interactive graphics such as where different air masses form; how global warming could raise sea levels; why lakes freeze from the top down; the life stages of a typical hurricane; how lightning creates thunder; the formation of hail; and more.

Animated Guide to Hurricanes

91 Simple Science Videos on Vimeo The aim of each video is to give a clear explanation of science topics that elementary and middle school students can understand.

 The Wild Classroom is a website that features a collection of podcasts and videos for science classrooms. One aspect of The Wild Classroom that impressed me was the Biomes of the World Map. The Biomes of the World map allows students to explore the map and watch an informational video about each

Science Magazine's Video Portal offers dozens of videos across a variety of topics in science. Each of the videos is connected to an article that you can read online or print for classroom distribution. The Science Interactives menu contains six interactive versions of posters they have published in recent years.

NASA's eClips videos are arranged by grade level; K-5, 6-8, and 9-12. There is also a section labeled for the general public. The videos are short clips designed to show students the work NASA is doing and how that work impacts space science as well as its potential impact on everyday life. All of the videos can be viewed online or downloaded for use on your local computer.

NASA Brain Bites is a series of videos designed to answer the questions the that kids typically have about the science of space travel and the "logistics" of daily life as an astronaut. Some the questions that are addressed include "what is the temperature of space?" and "how do you go to the bathroom in space?" All of the videos in the NASA Brain Bites collection can be viewed online or downloaded as QuickTime or Windows Media files.

Knotebooks you can organize information to create a reference article for yourself or to share with others. You can also browse the articles published by others, add them to your account for later reference, and or alter the articles that others have written to suit your needs. For example if I find and article in Knotebooks about Newton's Laws but some parts of the article are too difficult for me to comprehend, I can click the option for "easier content" and Knotebooks will change the article to meet my needs. Knotebooks is a great concept, learn more about it and see it in action in this video.

 Night Zoo Keeper  Users design an animal, either based on a real animal or something completely new. Then they write a profile bio for the animal and upload pictures. Then users are encouraged to write a story about their creature. There are also games and activities to play once you have signed in.

Learn Chemistry The purpose of Learn Chemistry is provide educators with resources for teaching chemistry lessons to students of all ages. The database of instructional resources is organized according to topic, age of students, and media type. A couple of resources for middle school and high school lessons that stand out are the Faces of Chemistry video series and the Visual Elements Periodic Table. The Faces of Chemistry is a set of short videos that explain how chemistry is an integral part of three fairly common activities; hair coloring, farming, and car exhaust control.