OmniGraffle for Mac
OmniGraffle is a comprehensive, yet easy to use diagramming and drawing application. Drag and drop to create wireframes, flow charts, network diagrams, UI mockups, family trees, office layouts, and more. OmniGraffle 7 comes with plenty of features to get started in Standard. OmniGraffle Pro has everything in Standard, plus features suited specifically for folks that make a living designing or working with graphics—things like Shared Layers, Artboard Layers, Non-Destructive Shape Combinations, Blending Modes and Fill Effects, Visio support, SVG export, and more.