Unicheck - The plagiarism checker Unplag scans across the internet, repositories, open sources content and databases. It delivers real-time results and has no cached data.
PlagiarismSearch - PlagiarismSearch is online service that detects plagiarized content.
Urkund - Detect and check for plagiarism with URKUND
iThenticate - Prevent Plagiarism in Published Works
PlagScan - The Internet makes plagiarism a bigger problem than ever.
Copyscape - Copyscape is a free plagiarism checker.