Of course the best sources of images and video for your projects are the ones you create yourself.
Images you find using GOOGLE or YAHOO image searches may be protected under copyright law. This page is designed to help you to find authentic images, and provide some great places to search for images to use in multimedia projects. Even you may not NEED to ask permission to use images found on these sites when publishing on the Web for educational purposes, you should cite or attribute these images to their creators unless otherwise notified! Copyright applies fully and automatically to any work -- a photograph, a song, a web page, an article, pretty much any form of expression -- the moment it is created. This means that if you want to copy and re-use a creative work you find online, you usually have to ask the author's permission.
THEREFORE when you create any work, you need to be aware of copyright issues.
It is good practice to look for copyright notices in any search and to be sure to read for further instructions.

What is Copyright?

Copyright Confusion

Copyright is designed not only to protect the rights of owners, but also to preserve the ability of users to promote creativity and innovation.
The Limitations on Exclusive rights (fair use of copyrighted material) according to U.S. Code Title 17 107 states that "the fair use of a copyrighted work for purposes such as criticism, comment, news reporting, teaching (including multiple copies for classroom use), scholarship, or research, is not an infringement of copyright. In determining whether the use made of a work in any particular case is a fair use the factors to be considered shall include
1. the purpose and character of the use, including whether the use is commercial or nonprofit
2. the nature of the use
3. the amount of the use
4. the effect of the use on the potential market for the copyrighted work."

Today, courts’ analysis of fair use issues tend to center on the question: Is the use “transformative?” Content creators need to consider what value their new work is contributing to the copyrighted material and whether their use is for a purpose different from that for which it originally was intended. The idea of "transformativeness" involves modifying material, putting material in a new context, or both.
This creates many misconceptions about Fair Use that we need to be aware of when creating educational content.

Get to know Creative Common

Share, Remix, Reuse — Legally

Creative Commons provides free tools that let authors, scientists, artists, and educators easily mark their creative work with the freedoms they want it to carry. You can use CC to change your copyright terms from "All Rights Reserved" to "Some Rights Reserved."
You can SEARCH for creative commons material and LICENSE your own work

Check out my information on

Digital Audio

Digital Images

Digital Video

For more information on finding copyright (copyleft) friendly sources and Web 2.0 tools
You may want to subscribe to the Copyright 2.0 podcast