If you want just a few pages on your website on SSL, just one page not on SSL, this plugin offers this possibility. In the settings you can add pages, posts, or any other post-type or even custom post types that you want to be on SSL. This plugin needs to be installed instead of Really Simple SSL, and is not meant to be an add-on.
You can take a look at the instruction video to see how the plugin works. Take a look at the demo site to see how a site can switch between SSL and non SSL with the help of this plugin.