Few days ago I've got a chance to get into beta test of a new duplicate content checker PlagSpotter which is told to be better alternative to Copyscape. After submitting couple of reports I've received an e-mail with a link to invite more people for closed beta test. As for now testing provides full functionality of future paid accounts for free and also promising some nice rewards for the most active testers. So, long story short - here is a link which you guys can go through and sign up to get some free cookies - http://www.plagspotter.com/customer/signup/?level=50&viptester=true. I found it to be somewhat better than Copyscape, but on other hand they still have things to work on. It seems like they are working really hard on it, because many things which I've reported to them got fixed in a very short time. Hope you get in before beta test goes down