I’ve placed two links about plagiarism on my English Themes For Intermediate/Advanced page.
The first one, called Plagiarism, is from Acadia University, and should be accessible to Intermediate English Language Learners. It’s an animated slideshow reviewing the problem.
The second one, called Academic Integrity, is from Ryerson University. It’s very well put together, and is basically a series of animated stories with text and audio support. The language, though, might only be accessible to advanced English Language Learners.