Emerson said that if you build a better mousetrap, the world will beat a path to your door. "Field of Dreams" told you that "if you build it, they will come." Both were wrong. Dead wrong.
You'll want to do all sorts of web-based promotion. But don't forget promotion in the physical world. Here are some things to do.
Make sure your web address is on everything -- your business cards, stationery, advertisements, signs -- everything. If you have separate entry pages for different groups of people, consider having stationery, cards and ads that mention the URL most valuable for them.
Issue a news release. It's true that having a website isn't really news in many areas anymore, BUT (it's a big but) that doesn't mean the news release won't work for you. Trade publications and smaller local papers often reprint the release. And you can mail it to your customers.
Don't just mail news about your site to your customers, if appropriate, use the new or redesigned site as the occasion for a sales call. Spend some time with your sales force working up a short presentation on the site that can be used on their calls. If they can get to show the site, they can ask to bookmark it on the customer's computer. Make sure they have leave-behind literature that spells out the benefits of the site for the visitor.
Make sure everyone who answers your phone knows about your site and the basics of how it works. Give them a short script to use to tell people about the site. Develop a simple information piece that they can send to folks who'd like one.
Consider a special promotion to draw folks to your site. I like promotions that offer something special to customers and prospects, but offer something that isn't much value to others.