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.
FlowMapp - FlowMapp is a UX planning tool for creating visual sitemaps and user flow.
Balsamiq - Balsamiq. Rapid, effective and fun wireframing software.
Octopus.do - Build your website structure in real-time and rapidly share it to collaborate with your team or clients. Start prototyping websites or apps instantly.
Moqups - The most stunning HTML5 app for creating resolution-independent SVG mockups, wireframes & interactive prototypes for your next project
DYNO Mapper - Create Sitemaps with the DYNO Mapper Visual Sitemap Generator.