There's a great post I wrote on my blog titled '75 Ways to Increase Your Site's Traffic'. Hopefully it could be of some help to you. Check it out: http://superbloggingtips.com/2007/07/75-ways-to-increase-your-sites-traffic/
I have had good experience with link exchanges with related websites. In the beginning I won't spend any cent in advertising or promoting the site. Just get the word out ... forum signatures, blog comments, forum posts etc!