UML is an essential tool in SE today. I’m especially interested in finding ways of introducing MDE to students and for that UML and OCL are an essential requirement.
I’ve been reading “Applying UML and Patterns”, 2nd Ed by Larman and I really like it. The site offers good resources, especially in the “diagrams” section. You can download Visio sources of the UML diagrams used in the book which are really helpful in creating presentations for courses.
You can find them here.