You may wish to try these alternatives:
Like TurnItIn, iThenticate is a service offered by Plagiarism.org, but is geared more toward professional writing and scholarly research. Publishers like Oxford University Press use iThenticate for its Cross Check software, which includes a database of more than 31 million articles and 67,664 books and journals.
Viper calls itself the "Free TurnItIn Alternative." It scans a large database of academic essays and other online sources, offering side-by-side comparisons for plagiarism. Note: Viper is available for Microsoft Windows users only.
PlagiarismChecker.com makes it simple for educators to check for copied work by pasting phrases from a student's paper into a search box. The system can search through either Google or Yahoo. Users can also use the "Author" option to check if others have plagiarized their work online.
Plagiarism Detect scans text at a rate of $0.50 per page. The system takes about 5-7 minutes per page, which makes for thorough examination. According to the website, Plagiarism Detect has recently updated its system with a new advanced algorithm, combining multi-layered technology and SMART scanning (which supposedly scans papers like humans).
Brian Klug created this plagiarism checker in 2002 as a student at the University of Maryland at College Park. The easy-to-use system allows users to paste entire papers into a search box. A premium version, for a subscription fee of $8, claims to increase the accuracy of the scan, and allows users to upload Microsoft Word documents.
Plagiarisma has a search box as well as a software download available for Windows. Users can also search for entire URLs and files in HTML, DOC, DOCX, RTF, TXT, ODT and PDF formats.
This minimalistic checker lets users search for text and upload TXT files.
CheckForPlagiarism.net claims its licensing fees are, on average, between 35% and 70% lower than competing services. Its basic account, meant for high school students, costs $20 and allows users to scan five documents. The service can scan multiple languages, and users can compare papers.
The EVE plagiarism detection system is one of the older services on this list, having performed almost 150 million scans since its creation in 2000. It runs users $29.99 for unlimited use and includes a 10-day money-back guarantee.