LetsEncrypt

https://letsencrypt.org/howitworks/

$ git clone https://github.com/letsencrypt/letsencrypt
$ cd letsencrypt
$ ./letsencrypt-auto --help
$ ./letsencrypt-auto --apache
IMPORTANT NOTES:
 - Congratulations! Your certificate and chain have been saved at
   /etc/letsencrypt/live/drew.invadelabs.com/fullchain.pem. Your cert
   will expire on 2016-05-15. To obtain a new version of the
   certificate in the future, simply run Let's Encrypt again.
 - If you like Let's Encrypt, please consider supporting our work by:

   Donating to ISRG / Let's Encrypt:   https://letsencrypt.org/donate
   Donating to EFF:                    https://eff.org/donate-le

Per domain:

./letsencrypt-auto run --apache -d drew-bg.invadelabs.com

 - Congratulations! Your certificate and chain have been saved at
   /etc/letsencrypt/live/drew-bg.invadelabs.com/fullchain.pem. Your
   cert will expire on 2016-07-09. To obtain a new version of the
   certificate in the future, simply run Let's Encrypt again.

SSLCertificateFile /etc/letsencrypt/live/drew-bg.invadelabs.com/fullchain.pem
SSLCertificateKeyFile /etc/letsencrypt/live/drew-bg.invadelabs.com/privkey.pem
Include /etc/letsencrypt/options-ssl-apache.conf