There are a lot of tools designed to help "sketch" business ideas and business models. You need to be able to define and refine your ideas with a pencil and paper at the best. Other tools like Business Model Generation are great at sketching and documenting business model assumptions. I'm a huge fan of Bill Buxton's Sketching User Experiences and you can find his talks at http://www.billbuxton.com/#talk

For UI work check out:

* http://www.onextrapixel.com/2010/09/29/40-brilliant-examples-of-sketched-ui-wireframes-and-mock-ups/
* http://webdesignledger.com/inspiration/18-great-examples-of-sketched-ui-wireframes-and-mockups

You goal is to be able to effectively communicate your ideas, your business and the next steps.