http://Medium.com

Publish informative articles and include a link back to your website within the content.

http://Quora.com

Participate in relevant discussions, provide valuable answers, and include links to your website when appropriate.

http://LinkedIn.com

Create a compelling LinkedIn profile and include links to your website within the "Contact Info" and "About" sections.

http://GitHub.com

Contribute to open-source projects and include a link to your website in your GitHub profile.

http://Blogger.com

Start a free blog and include links to your website within your blog posts.

http://WordPress.com

Similar to Blogger, create a free blog on WordPress and link back to your website within your content.

http://Tumblr.com

Publish engaging content on Tumblr and include links to your website within your posts.

http://Reddit.com

Participate in relevant subreddits, share valuable content, and include links to your website when appropriate (but be careful not to spam or violate subreddit rules).

Business directories

Submit your website to reputable business directories like Google My Business, Yelp, Yellow Pages, and Bing Places.

Social media profiles

Include links to your website in the bio or "about" sections of your social media profiles such as Facebook, Twitter, Instagram, and Pinterest.

Remember, while these websites can provide free backlinks, it's crucial to focus on the quality and relevance of the backlinks rather than just quantity. Ensure that the websites you choose are relevant to your niche or industry, and always aim to provide valuable content or contributions to maximize the impact of your backlinks.