1)   Sequence Diagram Editor 1.6
Modeling tool that simplifies and speeds up the creation and maintenance of UML sequence diagrams and telecom/wrieless call flow diagrams. It automatically takes care of layout and formatting (across multiple pages if needed).
sequence diagram, call flow, UML,

 2)   UModel 2008
Altova UModel 2008 Enterprise Edition is the starting point for successful software development. Visually design application models and generate code or reverse engineer programs into UML 2 diagrams. It's the simple cost-effective way to draw on UML.
UML, unified modeling language, application models, OMG, model driven architecture, data modeling, UML 2.1, software design, use case diagram, class diagram,

 3)   EventStudio Sequence Diagram Designer 2.5
EventStudio is a CASE tool for Sequence Diagram, Call Flow, Message Sequence Chart, Use Case and Collaboration Diagram Generation. EventStudio goes beyond UML sequence diagram support and supports advanced constructs for Systems Engineering.
sequence diagram, call flow, message sequence chart, UML, interaction diagram, use case, collaboration diagram, context diagram,

 4)   Trace Modeler for UML Sequence Diagrams 1.0
Trace Modeler is an easy to use and smart editor for UML sequence diagrams... It instantly updates the diagram layout, freeing you to focus on the actual content... Ideal for documenting existing systems and brainstorming new designs.. And fast too!
UML, sequence diagram, editor, interaction diagram, tool, easy, fast, modelling, modeling, model,

 5)   Altova UModel Professional Edition 2008
Altova UModel 2008 Professional Edition is the simple cost-effective way to draw on UML. Visually design application models and generate code or reverse engineer programs into UML diagrams. It's the starting point for successful software development.
UML, unified modeling language, application models, OMG, model driven architecture, data modeling, UML 2.1, software design, use case diagram, class diagram,