We just paid for this service and I must say it is awesome!!! It is a wonderful way to collaborate with students as well as hold them accountable. There are peer review and web2.0 options.
Turnitin (also known as Turnitin.com) is an Internet-based plagiarism-detection service created by iParadigms, LLC. Institutions (typically universities and high schools) buy licenses to submit essays to the Turnitin website, which checks the document for plagiarism.
Students may be required by schools to submit essays to Turnitin, as a deterrent to plagiarism. This has been a source of criticism, with some students refusing to do so in the belief that requiring it constitutes a presumption of guilt. Additionally, critics have alleged that use of the software violates educational privacy and intellectual property laws.
Parent company iParadigms, LLC, also offers a similar plagiarism detection service for newspaper editors and book publishers called iThenticate, and run the informational website Plagiarism.org. Other services marketed under the Turnitin brand are aimed at the educators' market, such as grade marking and peer review services.
Checkout the User Guide and ACHS website...