The Common Content project attempts to gather links to as much open content

Open content

Open content or OpenContent is a neologism coined by David Wiley in 1998 which describes a creative work that others can copy or modify. The term evokes open source, which is a related concept in software....

 as possible under the Creative Commons

Creative Commons

Creative Commons is a non-profit organization headquartered in Mountain View, California, United States devoted to expanding the range of creative works available for others to build upon legally and to share. The organization has released several copyright-licenses known as Creative Commons...

 parametric license regime. This includes both Share Alike and "NoDerivs" content, under both commercial and "no commercial use" terms, and so is not open source

Open source

The term open source describes practices in production and development that promote access to the end product's source materials. Some consider open source a philosophy, others consider it a pragmatic methodology...

 by the usual definitions.

There is an effort to build an effective interface to this content at the Creative Commons wiki which is a mediawiki-based service.