Here is a list of 20 websites where you can submit guest posts for free:

1. Medium
2. Quora
3. LinkedIn
4. Scoop.it
5. Tumblr
6. WordPress.com
7. LiveJournal
8. Blogger
9. Ghost
10. Typepad
11. Wix
12. Weebly
13. SquareSpace
14. Jimdo
15. Yola
16. Webnode
17. Webs
18. Site123
19. Wix
20. Weebly

Please note that while these websites allow guest posting, they might have certain guidelines and restrictions that you need to follow. It's always a good idea to review the guidelines of each website before submitting your guest post to ensure that it meets their requirements.