LucidChart - LucidChart is the missing link in online productivity suites. LucidChart allows users to create, collaborate on, and publish attractive flowcharts and other diagrams from a web browser.
Sketch - Professional digital design for Mac.
Moqups - The most stunning HTML5 app for creating resolution-independent SVG mockups, wireframes & interactive prototypes for your next project
Inkscape - Inkscape is a free, open source professional vector graphics editor for Windows, Mac OS X and Linux.
OmniGraffle - OmniGraffle is for creating precise graphics like website wireframes, an electrical system designs, or mapping out software class.
Adobe Photoshop - Adobe Photoshop is a webtop application for editing images and photos online.