The Pencil Project
The Pencil Project’s unique mission is to build a free and opensource tool for making diagrams and GUI prototyping that everyone can use.
Top features:
* Built-in stencils for diagraming and prototyping
* Multi-page document with background page
* On-screen text editing with rich-text supports
* PNG rasterizing
* Undo/redo supports
* Installing user-defined stencils
* Standard drawing operations: aligning, z-ordering, scaling, rotating…
* Cross-platforms
* Adding external objects
* And much more…Pencil will always be free as it is released under the GPL version 2 and is available for virtually all platforms that Firefox 3 can run. The first version of Pencil is tested against GNU/Linux 2.6 with GTK+, Windows XP and Windows Vista.
http://www.evolus.vn/Pencil/Home.html