Creative Commons is an organisation founded in 2001 with the aim of creating copyright licences that you can use to make it easy for others to share and build on your work. Some videos explaining it are available.
For example, if I has written some music that I wanted people to feel free to listen to and use in their own work (e.g. in videos) I could apply a Creative Commons licence to it. I could then make it available on a site with other music that has been given a similar licence. Examples of Creative Commons music sites are Jamendo and Magnatune.
Recently an educational division - ccLearn - has been started with the same sort of focus. It's mission is "minimize barriers to sharing and reuse of educational materials — legal barriers, technical barriers, and social barriers."
My hope is that this and similar projects that we could get involved with, will help us to use and develop resources that would otherwise be too difficult and time consuming to develop, by building on others work. For example the educational potential of games is very interesting (see James Paul Gee's book as a good introduction), but at Edge Hill we cannot really find the time to develop them by ourselves.
For more links and resources about open education resources, have a look at the Wikipedia OER page.