Creative Commons has built a series of open source tools to assist end users in publishing and use of CC-licensed media. For more tools, including some developed by third parties, see Category:Tools.
CC Lookup is a tool to verify embedded license information. MP3 files tagged with ccPublisher carry information about what license was chosen for the file and a public URL where the license can be validated. If you've downloaded an audio file from the Internet Archive or a P2P network like Morpheus that claims to be Creative Commons licensed, this application will verify that for you. ccLookup is licensed under the GNU GPL.
We have extensions for Mozilla-based browsers (including Firefox), to enable viewing of Creative Commons licenses within your browser automatically.
http://search.creativecommons.org provides a unified interface to CC-enabled web and media-specific search engines.