UML CASE tool - UML diagrams, use case modeling, reverse engineering and more...
BS Editor: Visual Paradigm for UML (VP-UML) is a user-friendly UML CASE tool that supports full software lifecycle - analysis, design, construction and deployment. The UML tool helps you build quality applications FASTER, better and cheaper. You can draw UML Diagrams, generate code from diagrams and vice versa, and generate documentation in different formats. The UML modeling tool also provides plenty UML resources including UML tutorials, UML demonstrations and UML projects.

Feature List:
+Full UML notation support (class diagram, use case diagram, sequence diagram, collaboration diagram, state diagram, activity diagram, component diagram, deployment diagram)
+OOAD support - object-oriented analysis (OOA), object-oriented design (OOD)
+Textual analysis for identifying candidate use cases, flow of events, classes...
+CRC (Class-Responsibility-Collaborator) diagram for finding objects
+Use case modelling (use case description, use case scheduling...)
+Business Workflow diagram - Process, Decision, Business Actor, Document
+Incremental round-trip engineering support
+Code Generation - generate code, model to code, diagram to code (UML to code, UML model to Java)
+Reverse engineering - code to models, code to diagram (Java to UML models, Java to UML diagram)
+Reverse engineering Java, C++, XML, Dot NET dll/exe, CORBA IDL
+UML Report generator
+Automatic diagram layout - rearrange shapes and connectors in diagrams
+Import/export XMI file
+Import Rational Rose project
+MS Visio Integration - draw UML diagrams with Visio stencils
+Export diagrams to SVG, PNG, JPG...
+Plugin and template
+Version control
+Multilingual support
+More...

Other UML CASE Tools / UML plugins:
Windows Platform:
+SDE for Microsoft Visual Studio .NET
Java Platform (Linux/Windows/Mac OS X):
+SDE for Oracle JDeveloper
+SDE for IBM WebSphere (WSAD)
+SDE for Borland JBuilder
+SDE for IntelliJ IDEA
+SDE for Eclipse
+SDE for NetBeans
+SDE for Sun ONE
+More SDE... you can free download Visual Paradigm for UML (ME) No Install 3.1 now.