The Catholic University of America Writing Center sets out clear guidelines about plagiarism for current students.

Indiana University discusses acceptable and unacceptable paraphrasing, as well as the usual questions about plagiarism.

Northwestern University focuses on accidental plagarism and the best ways to avoid it, with examples.

This tutorial will help you avoid plagiarism by providing examples that explain how to properly include in one’s own scholarly work information from other sources.

University of North Carolina at Chapel Hill has very clear and basic guidelines.