Tor Browser enables secure, anonymous web access to help bypass various forms of censorship and tracking. It includes the Vidalia Tor client along with Firefox ESR, as well as a variety of configuration changes including the NoScript and HTTPS Everywhere add-ons to enhance privacy. The official browser bundle from the makers of Tor.
Note that the Tor site has some additional precautions that careful users may wish to follow.
Functional in 64-bit. Cross-platform with clients available for Mac and Linux.