I'm a UI/UX designer. I work on wireframes (low fidelity UI mockups) every day. I specialize in mobile apps, but also work on web and desktop apps. Cheap/free tool (since work pays for my software): MS PowerPoint or any presentation app. You can easily sketch up a low fidelity design concept that gets the point across. Plus, you can embed hyperlinks so that clicking on an object goes to a different slide. Windows Apps: Traditionally, I've used MS Visio. Lately, I prefer Balsamiq. Both tools allow you to embed hyperlinks. With Visio, you can export your multi-canvas doc to HTML. With Balsamiq, you can export to PDF. By embedding hyperlinks, you also get a cheap "clickable mockup/prototype" of your concept. - Balsamiq: http://balsamiq.com[^] Mac Apps: On Mac, I prefer using Omni Graffle Pro or Balsamiq. Both have pluses and minuses. Graffle Pro has a great "shared layer" feature so I don't have to keep copying and pasting the screen backgrounds between canvases. Again, I always embed hyperlinks to export into a "clickable model" format to convey a user experience concept with colleagues. - Omni Graffle Pro: https://www.omnigroup.com/omnigraffle[^] Pro Tip: For any of these apps, I've found that it's best to create a separate panel object with no fill and no line (100% transparent). Then embed the hyperlink in the transparent panel object. It's much easier to move it around and always move it to the top Z layer, plus edit or delete it without affecting the main GUI components. Lately, I've been experimenting with Indigo Studio, as well. Indigo Studio isn't quite mature enough yet to replace one of the above wireframing tool, but it's promising. - Indigo Studio: http://www.infragistics.com/products/indigo-studio[^] I've also been experimenting with prototyping apps on mobile phones. First, exporting individual wireframes as PNG files, then wiring them up in a prototyping tool. Two good ones we've been trying are Marvel and Prototyping On Paper (POP). You can import each image, then easily put in hyperlinks to