As of this evening (June 28 in California), Let’s Encrypt has issued over 100,000,000 certificates in total.
ISRG post: https://letsencrypt.org/2017/06/28/hundred-million-certs.html
EFF post: https://www.eff.org/deeplinks/2017/06/lets-encrypt-has-issued-100-million-certificates
Let’s Encrypt stats: https://letsencrypt.org/stats/
Thanks to everyone who’s helped make this milestone possible, including the community here on this forum!