The important thing is to use them if you can to attract visitors. Though they are a lot of work, message boards and chat rooms can give results. You may want to try some ideas that my or may not be right for your site, just try to decide if the idea will be useful or take up space. For sites with large quantities of content, a search feature or site map will be useful to your users. For sites that sell on the internet, you should have some items or attractions that are free to all.
Free samples are useful and easily promoted.
It all depends on what you are trying to sell and who you want to come to your site. You should not rely on the natural content of your page. Try to open up to a broader yet related subject to give prospective visitors a chance of finding you. Also, be sure to give your visitors that come for your natural content something like a chat room, message board, or other useful attraction. Most importantly, be sure you can keep up with whatever you add to your site, and not let it get out of control.