What is Creative Commons? 

Creative Commons (cc) licenses enable the owner of a work to allow another party to re-use, adapt, and re-create with their work.  Different types of CC licenses allow for different levels of re-use.  Some stipulate that a work may only be used in non-commercial settings.  You can look at the license to find out how the work may be used. This article from the MakeUseOf blog describes what creative commons is and how and why to use it. If you have other questions about copyright, please see the Copyright FAQ

Audio

This is a list of sites put together by creativecommons.org.

Better With Music - http://betterwithmusic.com/
"Betterwithmusic.com is a Javier Suarez (jahzzar) project which offers original music conceived for use in all kinds of projects: films, short movies, animations, documentaries, advertisment, corporate image, multimedia, TV, radio… and of course, for download and personal use (and enjoyment)."

Creative Commons Music Search

If you are looking for music to serve as the background of a presentation or project, you can search for creative commons licensed music by visiting the Creative Commons website.  You can search for music by keyword, genre instrument or style.  Most of the music you will find can be downloaded and used for free. some other resources you can investigate are:

The Freesound Project http://www.freesound.org/ - This website features sounds and clips.  If you need some ambient or environmental sounds to add to your recording, this is the place to find it.  You will need to create a log-in to be allowed to download content, but they will not sell your information or spam you.

Jamendohttp://www.jamendo.com/en/ - This website features creative commons licensed music for you to download. You can search by mood, genre, geographic location, instrument and more.

Vimeo Music - Vimeo now offers a music search service for you to find music for your videos. This link will take you to a page with instructions on how to get started. The videos below will share about the service.

Other Resources

Images

freedigitalphotos.net http://www.freedigitalphotos.net/
From their site - "Download free and premium stock photos and illustrations for websites, advertising materials, newspapers, magazines, ebooks, book covers and pages, music artwork, software applications and much more. All our free images are of high quality, produced by our community of professional stock photographers and digital illustrators." In Most cases the free download will require a specific attribution. You can read more about that here.

Google Image Search

You can search for images that can be re-used from within a Google image search by doing an advanced image search.

Google Advanced Search
  1. Navigate to images.google.com. Enter a search term, press enter.
  2. On the first results page, click the gear icon located on the right-hand side of the page; select "Advanced search".
  3. Click the drop-down menu beside "Usage rights"
  4. Select "free to use or share". 
  5. Click the Advanced Search button.
Flickr Image Search
You can search for images that can be re-used from within a Flickr image search by doing an advanced image search.

Flickr Advanced Search
  1. Click "Advanced Search" beside the Flickr search bar.
  2. Scroll down the page and then select the "Only search within Creative Commons-licensed content".
  3. Any results from your image search will be labeled for re-use.
Other Resources
http://www.istockphoto.com/
http://www.sxc.hu/
http://worldimages.sjsu.edu/