Let's Encrypt
It’s finally here. Well, it’s still in beta and invite-only, but it works. Let’s Encrypt will give you free trusted certificate for your HTTPS server and provide an easy script to verify, obtain and renew it.

So far only Apache is fully supported, so if you use NGINX or Lighttpd you’ll have to configure it manually. Which is not a big deal, especially if you were using TLS with self-signed certificate before.

The only trick was that one has to use fullchain.pem for ssl_certificate in NGINX config (possibly the same applies to Lighty). After that the certificate was accepted by all my browsers on both Linux and Android: https://glsk.net.