iThenticate - Prevent Plagiarism in Published Works

tinySpell - A spell-checker for Windows. Checks text in clipboard and/or on the fly in any Windows program. Small and easy to use. Resides in the taskbar notification area. Free download.

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.

Hunspell - Hunspell is the spell checker of LibreOffice, OpenOffice.

PlagScan - The Internet makes plagiarism a bigger problem than ever.

GNU Aspell - GNU Aspell, usually called just Aspell, is a free software spell checker designed to replace Ispell.