In SEO world, building a site with high-quality content is much more effective than link building campaign. To constantly provide great content, we need source of free content (images, video, music).Tool Name: Creative commons search Or Google Advance Search
Type: Online Tool
Features: A greate places to find free content, share, use and remix. Either for commercial use purpose, modify or build upon.
Access the tool: http://search.creativecommons.org/ or http://www.google.com/advanced_search