The Tor Project and Electronic Frontier Foundation(FCC) brings a Firefox Extension Called “HTTPS Everywhere” which encrypts your communication with Major Websites..
At Present, Though Many of The Sites support Encryption over https the effect is Limited as almost all of the Websites have made Unencrypted http as default.
This Firefox Extension “HTTPS Everywhere” makes Everything https for the supported Websites.. That means it rewrites the requests and makes sure that https is default.
Download / Get “https Everywhere” Extension for Firefox here
Google, Wikipedia, Facebook, Twitter, and Identi.ca are few of the Sites which supports https everywhere. The extension forces your connection to HTTPS every time you try to access one of those sites