The Web is so big that you have to direct people to your site. Do it every chance you get. Put your URL on your business cards, letterhead, line sheets, ads, signs - every publication you make. Let them know that you use your site to show what's going on in your business.
Announce your site to them by letter, by email, by phone. Let them know when you've posted news that's important to them - new products, new people, new services, new facilities - anything you want them to know about your business.
Email is the best way. This means you must have an email address list. I can help you build one.