entrepreneur.com - look under tools and services, some great templates.
SCORE (as answered previously) is great as well, specially the fact that you can post questions for answers to your unique situations, from lawyers, accountants, etc.
For Web start up create a Alpha\Beta first then start planning your business once it gains traction. If you must pull together a plan early - go to www.garage.com/resources/ where you will find Guy Kawasaki's stuff like "Writing a Compelling Executive Summary".
Also start applying to competitions like TechCrunch50 and incubators like YCombinator. You will answer questions going through the heads of the best in the business and create deadlines\milestones to really get up, going and humming.