Web Form Mockup Tool Free. A streamlined web app that helps you create and collaborate in real time on wireframes mockups diagrams and prototypes. Protopie is a mockup tool dedicated to seamless and user friendly website mockup creation in a matter of minutes with no coding knowledge required whatsoever.

It is offered once as a desktop application locally installed on the pc and then continues as a web application. Easily create web and mobile app prototypes and wireframes with justinmind ui prototyping tool. Create a free account no credit card required.
Pencil project is a free and opensource firefox addon for designing gui prototypes.
You can test both versions free for 30 days before deciding on a payment version. Turn decisions into visual mockups without coding. Mockingbird wireframe online tool mockingbird offers its wireframing tool as a saas application. One can even share their projects in png or psd format.