Promote your site offline, too. Give out business cards with your URL, include your URL on stationary, etc. Participate in discussion boards and lists actively. If you continuously submit useful information and responses to other peoples' questions, you could gain targeted traffic from your signature. Let your existing visitors refer their friends to your site.
Word of mouth is still a powerful promotion tactic.
Use contests to boost site traffic, newsletter subscriptions, or other information gathering. Give away something free and submit your site to freebie sites. Include your site's name, description, and URL in every email you send. Find sites related to yours and offer the owners to trade links with you. If you have advertisements or affiliate programs throughout your site, try to integrate them into the design and content.