Software Ideas Modeler

Software Ideas Modeler is a lightweight and powerful tool for the creation of UML diagrams and some other diagrams. It supports 13 types of UML diagrams, Mixed Diagram, Data Flow Diagram, Entity Relationship Diagram, Requirement Diagram, User Interface modeling and CRC Card Diagram.
Software Ideas Modeler is freeware (also for commercial-use).
Main features:

• Fast and easy drawing of diagrams
• 13 types of UML diagrams
• 6 types of other diagrams (Data Flow, Mixed, CRC, Requirement, UI, ERD)
• Diagram styling
• Export to EMF, WMF, SVG, PNG, PDF
• Source code generating (C#, VB.NET, SQL DDL)
• Documentation generating

Link
Software Ideas Modeler from Home Page