UXpin - Design is really about solving problems. UXPin is the UX Design Platform that gets that right.
Balsamiq - Balsamiq. Rapid, effective and fun wireframing software.
Invision - Prototyping and collaboration for design teams
Moqups - The most stunning HTML5 app for creating resolution-independent SVG mockups, wireframes & interactive prototypes for your next project
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.
Axure - The most powerful way to plan, prototype and hand off to developers, all without code. Download a free trial and see why professionals choose Axure RP 9.