iThenticate - Prevent Plagiarism in Published Works
Mendeley - Easily organize your papers, read & annotate your PDFs, collaborate in private or open groups, and securely access your research from everywhere.
Turnitin - Turnitin is preferred by educational institutions around the world for preventing plagiarism. Instructors at all levels of education can request that students use the service to submit papers, and Turnitin checks those papers for plagiarism.
Zotero - Zotero is a free, easy-to-use tool to help you collect, organize, cite, and share research.
PlagScan - The Internet makes plagiarism a bigger problem than ever.
Qiqqa - Qiqqa is a free research and reference management software. It can be used in many organizational projects from the academic to the personal to the business endeavor. Read more about Qiqqa.