The Let's Encrypt client is now called Certbot and has a new home with EFF.
More information can be found here:
https://www.eff.org/deeplinks/2016/05/announcing-certbot-new-tls-robot
Additionally, EFF has launched a new website for the client found at:
https://certbot.eff.org
The main feature of this new website is interactive documentation. After
inputting your OS and webserver, it gives you the specific instructions
you need to get up and running with Cerbot. Try it out and let us know
what you think!