William P. Davis

This plugin allows you to force certain pages to display as SSL-only by simply checking a box. Please note, you must have SSL configured on your server and require SSL for either login or admin.

Define SSL Pages

Allows you to easily require SSL for specific pages.

Blucube

If your site has an SSL certificate you might find that you can access the site via both SSL (https) and non-SSL (http) URLs. This is a bad idea for security, and for SEO, as it can look like duplicate content on different URLs.
The answer to this is to redirect requests to non-SSL (http) URLs over to their SSL (https) equivalents using something called a 301 redirect. This tells the client (and search engines) that the resource they are looking for should always be accessed over SSL. This plugin offers two methods to achieve this:
<ul>
<li>By intercepting WordPress pages at header time, and if they are not already being requested over HTTPS sending a 301 redirect header, or</li>
<li>By adding mod_rewrite rules in the .htaccess file to redirect all requests to their HTTPS equivalents using 301 redirects.</li>
</ul>
Optionally, this plugin can also set <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Strict-Transport-Security" rel="nofollow ugc">HSTS</a> headers for you, and make sure that all requests use the same hostname (i.e. fixing the issue where many sites can be accessed using both www. and non-www. URLs).

Simple SSL Redirects

Lightweight plugin to ensure access via SSL/HTTPS. Uses 301 (permanent) redirects for SEO benefits. Optionally sets HSTS and forces canonical domain.

Define SSL Pages vs Simple SSL Redirects