Most people access the Internet for information on products and services that they either use now, or are considering buying. So, your Web site can be a great place to provide ongoing customer support for your products. If you're worried about giving away trade secrets to your competition, place these in a password-protected area.
The best way to build your content is to compile a list of questions that your customers most often ask. These may be sales related, but can also cover operations, quality assurance issues, etc. If you don't already know the questions, have your receptionists and sales people keep a note pad for a week. Then, put the questions, together with the answers, on your site.
This provides a 24 hour a day, seven day a week availability of service for your customers, whether your office is open or not. And, it can save significant costs in terms of telephone support time.