A few months ago at the Product Mavens Meetup we were discussing prototyping and wire framing to get ideas and concepts across different members of a team. It helps with design planning, development and overall strategy of a design or concept. It is also particularly good when working with clients trying to map out their structure of their websites. Having such a plan to work with makes development and implementation a breeze. One such tool that was mentioned was OmniGraffle for the iPad. Just recently the other week I stumbled across it as a Mac application as well and it looks quite nice.
The idea is that OmniGraffle allows you to create a visually appealing mockup, mind map or wireframe quickly and effortlessly. Further more it exports smoothly into more advanced and complicated programs like Microsoft Viso for further work. As mentioned at the Product Mavens Meetup, we find that the best part about wire framing is the engagement of the client in this part of the process. Being able to sit down with a client and quickly piece together their key elements, functions and primary layout with them really connects the design and development process with the client. If you're already doing this process or are starting to, I highly recommend looking into OmniGraffle for both the iPad and the Mac.
Thank you to Michelle Rowan for recommending it.