Lucidchart
Online diagram and flowchart software that supports Microsoft Visio import and can work on any operating system.
Mockup Designer, built with Backbone, Backbone-LocalStorage and Html2Canvas, is a super-easy-to-use mockup tool that uses the local storage of your browser as its...
Mockup Designer, built with Backbone, BackboneLocalStorage and Html2Canvas, is a supereasytouse mockup tool that uses the local storage of your browser as its backend. However the data layer is loosely coupled, so you can integrate with any RESTful API or any Backend service.
mockups prototyping wireframes wireframe-prototype wireframe prototype design prototypes
Online diagram and flowchart software that supports Microsoft Visio import and can work on any operating system.
Freemium
Pencil is a standalone app or Firefox extension that lets you create diagrams or UI mockups. It doesn't have collaboration/multi-user features.
Free Open Source Mac OS X Windows Linux Firefox Electron / Atom Shell
Using Balsamiq Mockups feels like you are drawing, but its digital, so you can tweak and rearrange controls easily, and the end result is much cleaner.
Commercial Mac OS X Windows Web
Free web and mobile mockup tool. Transform your design and mockups into clickable interactive applications. Perfect way to validate ideas faster with lean startup thinking. Best tool for quick prototyping.
Freemium Web
Justinmind is the best solution to prototype any web or mobile app you can think of. You can define websites and apps for Web, iOS, and Android with our intuitive...
Commercial
WireframeSketcher is a software tool that helps quickly create wireframes, mockups and prototypes for desktop, web and mobile applications. It comes both as a plug-in...
Commercial Mac OS X Windows Linux Eclipse
MockupTiger is a web based application that helps you to build fluid wireframes, mockups or prototypes for your next web application or desktop software. It has a...
Commercial Windows Linux Android iPhone Web
Prototype cheaply and quickly for iPad, iPhone, Android, Windows Phone 7, Facebook and web using Apple Keynote, Microsoft PowerPoint or OpenOffice Impress.
Commercial Web