Storyboarding is a part of a planning process. It is used in movie making and also in planning web sites and other functions where organizing a plan is needed before implementing a project. One would do well to story board their web site so as to know what it would look like, know where to place links, set up the hierarchy, and make the web site easy to navigate and appeal to as many people viewing it as possible.
Here are several web sites that will be helpful tutorials to guide you in the process of storyboarding.
Web Host Design Post
Conqueror Web Design
Cyber Sierra Workshop
Multimedia Journalism Berkeley