My coworker(his blog is located here) pointed me to this tool and I found it very useful.Quick Sequence Diagram Editor is a tool for creating UML sequence diagrams from textual descriptions of objects and messages that follow a very easy syntax.
Below you may see a syntax example for Sequence Diagram shown in screenshot – it’s very intuitive and easy to understand.
The tool supports actors, constructors, destructors, threads and on-diagram comments that can be used to represent conditions or loops.
Diagrams can be exported in PNG format.
Please choose a file named "sdedit-light_no_export_library.exe" to run the sdedit on a Windows Platform. The exe file is wrapped around a Java archive (you still need Java 5 or higher).)