The comodo SSL certs via https://ssls.com are very cheap. Install instructions for a Nginx based webstack:

Create signing request:

cd /etc/nginx/ssl
mkdir example.com
cd example.com
openssl req -nodes -newkey rsa:2048 -keyout example.com.key -out example.com.csr

Copy paste the content of the csr on ssls.com, choose webserver other.
Fill out the next page with info about your organisation.

You’ll receive a zip with a bunch of files. Copy the files to the webserver

scp * root@server:/etc/nginx/ssl/example.com/

Login on the server and go to /etc/nginx/ssl/example.com/
Now create the bundle_ssl.crt

cat example_com.crt COMODORSADomainValidationSecureServerCA.crt COMODORSAAddTrustCA.crt >> ssl-bundle.crt

Add to conf (I already had SSL running with fake certifcates)

ssl_certificate         /etc/nginx/ssl/example.com/ssl-bundle.crt;
ssl_certificate_key     /etc/nginx/ssl/example.com/example.com.key;
ssl_prefer_server_ciphers on;
ssl_session_cache shared:SSL:10m;
ssl_session_timeout 10m;
ssl_ciphers ECDHE-RSA-AES256-SHA:DHE-RSA-AES256-SHA:DHE-DSS-AES256-SHA:DHE-RSA-AES128-SHA:DHE-DSS-AES128-SHA;
ssl_protocols SSLv3 TLSv1 TLSv1.1 TLSv1.2;
keepalive_timeout    70;

More info:
https://gist.github.com/bradmontgomery/6487319