Its hard to find a good free one. I've look around and I've been a long time user of Balsamiq. But it like the possibility to easily make an interactive/useable

Its hard to find a good free one. I've look around and I've been a long time user of Balsamiq. But it like the possibility to easily make an interactive/useable mockup. I've switched to Protoshare ( http://www.protoshare.com http://www.protoshare.com ) and you can easily create full fledge prototype that can be actually used/tested. Check the video on their landing page. Pricing wise it's 29$ / Month Cheers