Mozilla launched a “free, automated and open” certificate authority called Let’s encrypt. As the name suggests, it provides free certificates trusted by all (major) browsers and operating systems. I’m using it heavily (on this blog, for example).
This blog post shows how Syncthing can be used to deploy letsencrypt certificates in an environment with multiple servers (e.g. in a round-robin scenario) without adding a single-point-of-failure.