Below are a list of links where you will be able to find royalty free and creative commons based music and sound effects. If you decide to use any of them, you must attribute the creators of the content. Any of the sounds or music can be used in your animations or videos.
Free SFX http://www.freesfx.co.uk
Sound bible http://soundbible.com
Media Collage http://www.mediacollege.com/downloads/sound-effects/
Free Music Archive http://freemusicarchive.org/curator/creative_commons/
Ben Sound http://www.bensound.com