Entrepreneur Magazine provides resources to help focus an individual through different parts of writing a business plan.
SBA Business Plans
The SBA's business plan page provides many links to helpful information for writing a business plan.
The website of SCORE – Counselors to America's Small Business includes a link to information on developing a business plan for a start-up business and a business plan for an established business. Each includes a template and expanded information on the process. In addition there are fourteen templates for other documents needed to create and/or maintain a business. The authoritative information found here is from an organization that is a resource partner of the federal government’s Small Business Administration.