Barter for advertisement. Use your website to help you obtain more marketing. For instance, if you have a highly targeted site you could barter with another site in order to piggy back off their traffic. You could place a banner or text ad on their site in exchange for them putting one on your site as well. In this instance, you both benefit and reach more visitors.
Utilize such companies like linkreferral.com. With that site, you register and promote your site in their directory and you receive indirect search engine traffic via their program. For instance, your directory listing and affiliate pages get traffic as well. This is a great way to increase your targeted traffic.