Balsamiq Wireframes

Tiggr is an application for creating user interface prototypes collaboratively online.

Sketch Lab is a web based user interface (UI) sketch / prototype tool. It supports desktop and mobile platforms.

Mockery enables you to create great UI mockups, quickly and easily. Design great interfaces for the web or desktop. Review your designs with Windows and Mac themes. Annotate your mockups …

POP helps you make interactive prototype with ease. If you can draw, you can design apps. The workflow is ridiculously simple: 1 Design on Paper 2 Take Pictures 3 Link …

MockupCreator is a tool to create mockups, prototypes and wireframes. MockupCreator will help you to accelerate your products development and improve the quality of the product design.

UIreframe is an online web-based tool that lets you create nice wireframes and mockups easily for your websites or software applications. With UIreframe you can collaborate and share your creations, …

Blueprint is an UI design application for iPad and iPhone

Mocklinkr is a web application that allows designers to: upload and host their mockups; link them together and make them interactive; and provide a mechanism for their clients to leave …

Mockups for Android is a vector-based sketch wireframing tool for web site prototyping and creating UI design concepts. With Mockups for Android, you can experiment with concepts and sketch visual …

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 backend. However the data layer is loosely...

Prototype cheaply and quickly for iPad, iPhone, Android, Windows Phone 7, Facebook and web using Apple Keynote, Microsoft PowerPoint or OpenOffice Impress.