Unified Modeling Language

Introductory tutorial on the UML notation and usage in software engineering. By Sparx Systems.

A complete reference which can be downloaded for off-line use, by Zvon.

A UML modeling tool that support round-trip engineering of C#, Visual Basic .NET, Java and C++. Integration with Visual Studio .NET and Eclipse. [Commercial, Free Personal Edition]

Cross-platform, easy-to-use UML editor integrated in the Eclipse development platform. [Open Source, GPL]

Supports popular modeling tools to improve functional design visualization and validation by directly executing UML domain models as web applications that include business logic. [Free, Open Source]