Anyone may choose a Creative Commons license by going to http://creativecommons.org/license/
Several services are available to integrate license selection into a website or application:
RESTful web services API
Allows any website or application to transparently integrate CC licensing. Used by CcPublisher.
Documented at http://api.creativecommons.org
Documented at http://creativecommons.org/technology/web-integration (to be moved to wiki)
Requires minimal knowledge of HTML.
Documented at http://lists.ibiblio.org/pipermail/cc-devel/2006-March/000083.html (to be moved)