Copyscape is built as a tool to research online plagiarism and is also useful if you are looking for duplicate content. We wrote about this tool in the past… but it has cropped up again recently as a tool to find duplicate content.
Simply type in the address of your web page, and Copyscape does the rest. Copyscape finds sites that have copied your content without permission, as well as those that have quoted you.
When you click on any link, it displays the webpage and highlights the text at issue:
If you are not trying to sniff out duplicate content or stolen content, this this is a fun tool to research yourself and your competitors.
Try searching some of the interior URLs of your websites too.
Please leave suggestions below if you have a different tool you recommend.
One question I cannot answer is how to do the same with videos, since, Copyscape only works with text. Again, leave any suggestions below.