Ian Dunn

Redirects all HTTPS traffic to HTTP, except for specific exceptions. You might want to do this to minimize the number of times users would see an error if you don’t have a valid SSL certificate setup, or if you want to make sure that the delay SSL adds is only experienced when necessary.

Force non-SSL

Redirects all HTTPS traffic to HTTP, except for specific exceptions

blackc2004

This plugin will make sure that all elements on a page are SSL if the page is being accessed via HTTPS. For this to happen you must have used correct programming practices and use siteurl, wpurl, url etc where all the locations are supposed to be.
Some plugins do not correctly use this, I have already notified a few of them, but you may find some other issues, if you do, please contact me and I will research and attempt to notify the developers of the other plugins.

HTTPS for WordPress

Check to see if SSL is used. This will update any template functions which require SSL to be used.

Force non-SSL vs HTTPS for WordPress