Well... So you don't want to pay for Adwords? :) hmmm

Here is what you should do:

1- Submit it to all the free search engines like Google, Yahoo, msn, and others...

2- Create a blog for your website, and post at least 1 entry/week.

3- Make your website's content available in RSS feeds.

4- Post your website everywhere on the internet.... forums, blogs, rss feed burners, and everywhere.

5- Make an invitation tool for your website, registeration system, and let users import their contacts to invite their friends to your website...

Try to make it social as much as you can... and update it's home page daily... that would be great.

Also don't forget to add rich information that would be really useful to users. Content is the king!

If you follow this recipe, you will have a good base of users within 6 or 7 months!