1. Give people a free subscription to your e-zine. Almost everyone is publishing a e-zine nowadays so it's important to give something extra with free subscription. You could offer a free gift or advertising when people subscribe.
2. Provide your visitors with free content. Your content will be more attractive to your visitors if it's up-to-date or original. You could also offer people option to reprint content in their e-zine or web site.
3. Offer a free online directory. The directory could be full of interesting ebooks, e-zines, web sites etc. If people find your directory to be a valuable resource they will visit it over and over.
4. Give your visitors a free ebook. You could also include your own ad in ebook and allow other people to give it away. If you don't want to take time to write one, you could ask other writers permission to use their articles.
5. Hold free online classes or seminars. They could be held in your web site's chat room. The idea of "live" information will definitely entice people to visit your web site. You will become known as an expert on topic.