Blog and Ping
Create a Blog you can install the blog on your own site or use a free blogger tool like Blogger.com. Update the blog everyday with content specific to your niche and a link back to your niche site. Ping the blog using a free pinging service like pingoat.com. This will update several services about new content at your site. The Search Engines will spider your blog and find your site.
Find other blogs related to your niche. Do a search on blogger.com for blogs related to your site. Leave very relevant comments with a link back to your site. Again people and the search engines will find your site. Do not leave worthless and spam comments on other blogs. Be a benefit to the blog community with good information.
Article submission to article directories is awesome. You can earn very valuable backlinks to your niche site. Ezine authors search articles directories for articles to publish in their ezines. Publish a good article and it could be published to thousands of ezine subscribers for free. Write a solid author bio with a link to your niche site. Websites and Ezine Publishers must publish your bio with the article. You will receive visitors from this effort.
There are specific places to submit articles to for massive visibility like GoArticles.com. You can use an Article Submission Service to mass publish your article on thousands of lists and article directories all over the web saving you time.
Find forums that allow you to post free ads. Better yet find forums related to your niche website. Answer questions on the forum including your signature line with your web link included. Also ask questions. Forums are not only great for posting your web link but can be great to get ideas on new articles to write.
Search Engine Optimization
Work on your Search Engine Optimization. Learn about on and off page optimization. Learn about keyword density, image alt tags, meta tags and link popularity. Search Engines are going to be a huge asset to driving traffic to your site. With a little effort you can find your niche site in the top 10 keywords.
Start a reciprocal link campaign with other web sites in the same niche. Trade links or simply ask for a link to your site. You can do this for free with a links directory script to manage your links.
Text links are keyword specific links to your web site posted on other sites. You can pay for these or you can set up trades as well.