Firefox: Inspired by Google's offering of an encrypted, HTTPS-connected search, the Electronic Frontier Foundation and the TOR anonymous router network have teamed up to create an add-on that encrypts your connection to Facebook, Wikipedia, other Google Services, news sites and more.
Install the add-on, and by default, everything's checked, and any time you hit one of the sites covered by HTTPS Everywhere, your browser automatically goes for the HTTPS/SSL connection option, or uses TOR's resources to make it encrypted. The add-on covers the New York Times, Washington Post, Twitter and Facebook, and a good many popular and semi-obscure sites. If there's a site with an encryption offering you'd like to see included, you don't have to wait for an add-on update—write your own ruleset and add it to the simple XML config file.
HTTPS Everywhere is a free add-on for Firefox only. Know of a popular site that's got a good encryption option? Share it in the comments, and maybe some of our craftier coders can also share a ruleset.
Encrypt the Web with the HTTPS Everywhere Firefox Extension [Electronic Frontier Foundation via BoingBoing]