Guest post on other blogs, and invite other bloggers to guest post on your site. Guest posts are a great way to drive traffic between related blogs, and allow you to gain readers that might not normally make it to your site. Be sure to allow any guest posters to link back to their own site, and share any guest posts the same as you would your own posts.
Social media is one of the most popular free marketing tools around, and plays a role in driving traffic to your website. Use Facebook, Instagram, and LinkedIn to promote blog posts and other useful pages on your website. This way you can turn your social media audience into website visitors, and draw traffic from their networks if you post shareable content.