• Franklin students can download Visio for free from ELMS
• uml.org, the OMG's UML page
• Allen Holub's UML reference card.
• Holub's site also has freely-downloadable UML templates for Visio 4 and 5.
• My all-time favorite UML book: UML Distilled, by Martin Fowler
• Visual Paradigm offers free UML drawing tool. The free version is fully-functional, and you can save diagrams, but you can have a maximum of one drawing of each type per project. The version I tried was huge - the download file was about 120MB, and after installation it's using about 190MB.
• Applying UML and Patterns, by Craig Larman

Examples

• Package diagrams for Model/View/Controller and the DVR system (used in week 2)
• Class and sequence diagrams about the Structural Model (used in week 5)
• Skeleton database for elections (used in week 6)