Try this on for size: Put up a banner ad (small, graphical advertisement on a website). You can use a pay-per-click service like Google AdWords, DoubleClick or Overture. These can generate a lot of traffic and can be very effective if used properly. These can also cost a lot of money, however, because you are paying per click and whether the visitor buys or not.
Another, less expensive option is to trade your banner with another (local?) company with which you already do business. For example- if you own a flower shop, you might trade a banner with a wedding planner. Put his banner on your website and your banner on his. By trading, you’re helping each other’s business and it won’t cost you a thing!