Avoiding Plagiarism - advice for using sources.
How to Lessen the Chances of Plagiarizing - from the Learning Skills Centre at the University of Northern British Columbia.
Plagiarism and the Art of Skillful Citation - essay on what plagiarism is and how to avoid it, especially in science writing.
Statement on Plagiarism - "To put your name on a piece of work is to say that it is yours, that the praise or criticism due to it is due to you." From WFU.