Trying to find some inspiration for my UI I reached http://www.balsamiq.com/. These guys have an impressive Mockup generator program called Balsamiq Mockups. It is quite easy to create mockup interfaces for your applications, and pretty easy to use. The best thing is that they offer a free license to oen source contributors (do-gooders as they call us ^^). I asked for one and they sent me a license in one day!!!!
Now I will start developing a mockup UI and publish it to have some comments about it.
If you want more info about balsamiq, click on the image below.