Really Simple SSL

With over 3 million active users and a rating of 4.9 average Really Simple SSL is our most used plugin.

Really Simple SSL automatically detects your settings and configures your website to run over https.
To keep it lightweight, the options are kept to a minimum. The entire site will move to SSL.

The free version can be downloaded here:

Really Simple SSL

There are also some add-ons available for Really Simple SSL:

Check out add-ons