HEATKEYS

PlantUML is an open-source tool written in Java that uses simple textual descriptions to draw UML diagrams. Can be integrated with Word.

ckwnc is a uml sequence diagram creation tool that uses an intuitive c-style language to automatically create uml diagrams that can be saved as an image or embedded directly into other pages

Web Development Tutorials, Tips and Tricks on ASP.NET, jQuery, JavaScript, .NET, LINQ, Open Source Tools, Silverlight, Visual Studio and much more

JUMLY must help you if you want some sequence diagrams in your web site. Without images and expensive heavy UML modeling tools, you can put sequence diagrams as easy as writing a few lines of JavaScript.