WebProNews

I personally use the http://www.copygator.com website to find duplicated content. To me it has a number of benefits over copyscape and copyrightspot:

1. it's automated and brings me results instead of me searching for duplicated content. All i had to do was submit my feed and it started monitoring my feed showing me who's republished my articles on the web.

2. i get notified by email so it contacts me when it finds copies of my articles online.

3. i use their image badge feature to alert me directly on my website when my content is being lifted.

4. it's a free service as opposed the "per page" cost of copyscape/copysentry.