1. Work on website SEO.
SEO stands for Search Engine Optimization and it's the best thing since sliced bread for promoting your website because it's easy to learn and apply the basics to your own website(s).
2. Reciprocal linking.
Having other people put a link to your site on their site is a great way to get free website promotion. Besides the obvious advantage of whoever visits that website seeing a mention to your site, you also get a shot at a better search engine ranking for your page as search engines such as Google use inbound links as an important part of the formula that determines a page's rank.
3. Write articles.
The basic theory of article marketing is that you write an article and then offer it for free to various websites, blogs, magazines etc. Your article, of course, ends with a resource box or 'blurb' that promotes you and your website.