A few weeks ago I read a tweet which brought me to Moqups.
What is it? A simple and useful HTML5 App used to create mockups, prototypes or whatever you need related to UI.
You have several objects called "Stencils", which represent user interface elements, such as Radio buttons, Labels, Text areas or even Date pickers and Audio/Video players. Some of them have configurable properties, others have editable content.
You also can upload your own images, undo/redo all your changes and export your mockups to PDF or PNG among other things.
Press F1 if you need to use the shortcuts and wherever you type in the app, you start searching the stencils.
You'll find all the news about Moqups in the Moqups team blog or in their Twitter
I've used it for simple things till now, just like the example below, but I really like it, for me is the most useful free tool I found recently.
Enjoy it!
Basic example using Moqups |