(Updated June 2012)
Archive.org – Known mainly for their “Wayback Machine” as a means for seeing old pages on the net, they have also collected together a huge collection of free-to-use recordings and texts.
Creative Commons Content Directories – Lists sites offering Creative Commons content in the form of audio, video, image, text and other.
Freebase – A community powered search engine to search the web for CC licensed work for you to use.
Google Advanced Search – Google gives you the option to include forms of licensing in your search.
Search Creative Commons – The domain search.creativecommons.org is not a search engine, but rather offers convenient access to search services provided by other independent organizations. Do not assume that the results displayed in this search portal are under a CC license.
Wikimedia Commons – The central clearing area for the Wikimedia projects CC files.
Yahoo Creative Commons Search – Yahoo allows you to search the entire web for what you need based on the licenses attached to the content.