Is what I used. It is easily installed from the repository:
Name: ObjectAid UML Explorer
And produces quite nice UML diagrams:
Description from the website:
The ObjectAid UML Explorer is different from other UML tools. It uses the UML notation to show a graphical representation of existing code that is as accurate and up-to-date as your text editor, while being very easy to use. Several unique features make this possible:
Your source code and libraries are the model that is displayed, they are not reverse engineered into a different format.
If you update your code in Eclipse, your diagram is updated as well; there is no need to reverse engineer source code.
Refactoring updates your diagram as well as your source code. When you rename a field or move a class, your diagram simply reflects the changes without going out of sync.
All diagrams in your Eclipse workspace are updated with refactoring changes as appropriate. If necessary, they are checked out of your version control system.
Diagrams are fully integrated into the Eclipse IDE. You can drag Java classes from any other view onto the diagram, and diagram-related information is shown in other views wherever applicable.