free-ssl, DV class is free for a bit of time, normally.

1. https://www.globalsign.com/ssl/ssl-open-source/
2. https://gethttpsforfree.com/
3. https://www.cloudflare.com/ssl/
4. https://sg.godaddy.com/zh/ssl/ssl-open-source.aspx
5. https://console.qcloud.com/ssl
6. https://letsencrypt.org/
7. https://www.sslforfree.com/
8. https://zerossl.com/free-ssl/
9. https://www.ssl.com/certificates/free/
10. https://www.instantssl.com/free-ssl-certificate.html
11. https://ssl.comodo.com/free-ssl-certificate.php
12. http://www.freessl.su/
13. https://www.geotrust.com/ssl/free-ssl-certificate/
14. https://www.positivessl.com/free-ssl-certificate.php
15. https://www.freessl.com/freessl/