As an entrepreneur myself, I understand that you may feel the need to start building right away...there is no time to test the concept with your customers or peers, right?. However, with so many easy to use tools out there to demonstrate your concept quickly, you'd be crazy not to gather feedback before coding.
One tool that's extremely helpful is Balsamiq Mockups (not an affiliate link). I've used it numerous times and it's one of the first stops I make when I think of a new idea.
Balsamiq enables you to quickly, easily, and at no-cost create a sketch of your website or mobile app that you can use to demonstrate to customers.
Examples of Fast Sketches
Balsamiq's interface is extremely easy to use. Here's a 2 minute video of how to create the main iTunes interface, demonstrated directly by the company founder.
In addition to sketching your idea for a new website or mobile app, you can use Balsamiq to work with your creative or development team in building a product to your specifications, wireframing website designs for clients prior to starting a project (if you design websites for people), and much more.
Try Balsamiq for Free
While there are quite a few awesome features within the paid version (not an affiliate link), there is plenty that you can do with the web-based demo linked from the homepage. You can sketch your entire app, download it as a jpg/PDF, and even save the sketch and open it at a later time.
Give Balsamiq a try and pick up the paid version if you find it useful. This team is absolutely killing it, on both their product as well as the great service they offer.
Do you have any other tools that you use regularly to concept your idea for people? List them in the comments.