You've created a logo, and a website.  Great! Now the client needs a business card, letterhead, a newsletter, brochure, a twitter background, oh, and they're going to be producing a series of DVDs, a podcast, and are asking you what you know about developing mobile apps!   Planning for all these places where the organization's message will be present has become increasingly more important to avoid technical headaches, but more importantly ensure that the brand is kept consistent and your design continues to look crisp and professional no matter where it's placed.