This Web site is a good one and provides you with services of planning, development, design and maintenance of web sites.
Patrick Lynch also has an entire section on targeting the audience that you want to see your site.
This is a great checklist about the planning of your own Web site.
This is a site that explains web planning step by step with links to better definitions.
A personal web page with good insight.
This is a well organized step-by-step to assist in planning a website, in the form of questions to ask yourself as you develop and plan.