If the content of your site has something valuable to offer a specific audience, then by all means find the appropriate newsgroups and mailing lists and let those people know about it. Use Advertising, Marketing and PR Traditional marketing methods can be highly successful, assuming you have the money to invest. If you decide to place print ads in various publications, make sure they are targeted to your audience. If your website is designed for classic car enthusiasts, don't advertise in a travel magazine. Be sure to include your site name and URL in all of your advertisements and marketing materials.
Advertising online is another way to go.
The rate is also determined by how highly targeted the audience is. For instance, if you are selling graphics software, you want to reach design professionals. If you advertise to a general audience, most of those people will have no interest in your product. So while it may cost more to advertise to a targeted audience of graphic artists, the chances are greater that they will have an interest in, if not buy, your product. We've saved the best for last.