The best way to get traffic ~ without paying for it ~ it to optimize your site for the search engines. If you are coming up on the first page of google for your keywords you will have great traffic.
You can also submit your site to stumbleupon, Digg, delicious and the rest of the social bookmarking sites. You may get some traffic from them, but you will get good backlinks which will help your rankings in the search engines as well. You can do a mini site (optimized for keywords) at squidoo, which should get you some decent traffic.
Never hurts to do some work at the social networking sites like myspace. That's how I got my newest site going. I had a lot of friends at myspace who were interested in the same topic. I posted bulletins and to my blog to that group of friends.
I also continue to post to my blog and bulletins when I update that site ~ so people will stop by and take a look. It's working pretty well.
It's only a couple months old and I have generally over 100 visitors a day, some days with a good stumble I'll get 6 or 7 hundred a day.