Pencil is a Firefox add-on to do GUI prototyping and simple sketching.
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…
MorganLighter
