Creative Commons has been described as being at the forefront of the copyleft movement, which seeks to support the building of a richer public domain by providing an alternative to the automatic "all rights reserved" copyright, dubbed "some rights reserved." ... Creative Commons has provided "institutional, practical and legal support for individuals and groups wishing to experiment and communicate with culture more freely."In a nutshell, when someone gives you "creative common" rights to an image or audio file, you can use it on your websites, presentations or what have you without worry of copyright violations. You can visit the Creative Commons website to learn more.
LicensesAbout The Licenses.
Creative Commons Image SitesCreative Commons Search - find the image you need with the proper rights in place.
Open Clip Art - great CC clipart.