The EFF, the Electronic Frontier Foundation, is known for standing up for web rights, privacy and so on. It's not known as a software developer, but it does have one project that would qualify it, the HTTS Everywhere add-on.
The add-on forces browsers to switch to encrypted HTTPS connections for the websites that offer support, even if it's not by default.
Regularly, browsers use whatever protocol you type into the box, given that they're supported. If you start a URL with HTTP, you'll get an HTTP connection, unless the website redirects you.
The problem is, of course, no one actually types URLs anymore, they find them in searches or in their history of bookmarks, suggested by their browsers. So they'll end up whatever version of the protocol is picked for them, most of the time the plain HTTP.
HTTPS Everywhere aims to fix that and the latest version, the 3.0 release, adds support for 1,500 more websites to the already impressive list. In total, the add-on supports over 3,000 websites at this point.
The EFF also boasts that the add-on is used by more than 2.5 million people, based on the number of downloads and update requests the add-on gets.
"Our current estimate is that HTTPS Everywhere 3 should encrypt at least a hundred billion page views in the next year, and trillions of individual HTTP requests," the EFF explained.
"Install HTTPS Everywhere today to protect your communications from prying eyes, your cookies from identity thieves, and your reading habits from censors," it added.
HTTPS 3.0 is available for Firefox users now available, via the dedicated page EFF provides. If you care about your privacy, you should grab it. You should note though that it could sometime interfere with normal website operations, especially if the website hasn't implemented HTTPS properly.