The RSA algorithm has become the de facto standard for industrial-strength encryption, especially for data sent over the Internet. It is built into many software products, including Netscape Navigator and Microsoft Internet Explorer. The technology is so powerful that the U.S. government has restricted exporting it to foreign countries.

A similar technology that is also used widely is offered by a company called Cylink.

RSA Data Security home page 
Site of RSA Data Security Inc, creators of the RSA encryption technology used in Netscape Navigator, Quicken, Lotus Notes, and hundreds of other products.

SSL Basics for Internet Users
A plain-English guide to frequently asked SSL questions.