It's impossible to talk about getting traffic without specifying what <i>type</i> of product you have. Is it a paid downloadable app, SAAS webapp, social network, etc?<p>Most forms of paid advertising aren't cost effective unless you have a very direct way to convert traffic quickly into money and have pretty high margins.
Just posted on Quora about a similar topic.<p>Here's what we did to launch Meeps:<p><a href="http://blog.meeps.com/post/4588034501/bb" rel="nofollow">http://blog.meeps.com/post/4588034501/bb</a><p>Got quite a lot of buzz and traction because it was something unique that tied into our core concept.
I don't know if I would recommend this but here is an article on generating traffic...<p><a href="http://news.nucleusdevelopment.com/2011/01/08/the-fool-proof-social-website-model/" rel="nofollow">http://news.nucleusdevelopment.com/2011/01/08/the-fool-proof...</a>