Wireframing

Using Balsamiq Mockups feels like you are drawing, but it's digital,

MockFlow has an enormous amount of objects, and some of them incredibly specific. When you create a new design, you can start from one of the design templates

MockingBird can help you create your wire-frames in a fraction of the time it’d usually cost you.

35 Excellent Wireframing Resources

An illustrated guide

Lumzy is fast to use. No downloads, no sending of files to clients. Simply click "Share" and your client sees the project on the other end, just as you created it, and can post comments back and forth iteratively.

The Pencil Project's unique mission is to build a free and opensource tool for making diagrams and GUI prototyping that everyone can use.

With hosted mockups, you never have to worry about emailing mockups back and forth. You and your client will always be looking at the same version of the same mockup.