The Plagiarism Court (Fairfield University) - A great way to gain an understanding of exactly what plagiarism actually is; plain-text tutorial and exercise. At the end of the quiz, you can have your score emailed to yourself!
Plagiarism: What It is and How to Recognize and Avoid
It – (From Indiana University)
Plagiarism* - a comprehensive site for students, for
instructors with case studies, tools for detecting, and articles.
(From Sharon Stoerger MLA, MBA)
Student
Resources, Plagiarism – among other resources
listed are articles, basics, and tutorials on what plagiarism is
and how to avoid doing it. (From RIT Libraries)