Tor (The Onion Router) is "a network of virtual tunnels that allows people and groups to improve their privacy and security on the Internet. It also enables software developers to create new communication tools with built-in privacy features. Tor provides the foundation for a range of applications that allow organizations and individuals to share information over public networks without compromising their privacy".
Tor not only lets an end user connect to servers on the "clear internet" via exit nodes, but also lets nodes (including desktop computers) proxy services (TCP ports they're listening to) as hidden services (also known as onion services), where the entire route between user and service is hidden from tracking and encrypted end-to-end.
- Facebook is available at https://facebookcorewwwi.onion – quite remarkably with a trusted HTTPS certificate for the .onion address! An article on the Tor blog describes it in detail.
- Keybase is available at http://fncuwbiisyh6ak3i.onion
- Greg V's https://unrelenting.technology is available at http://fusrodahw6jpucw6.onion
- Marty McGuire's https://martymcgui.re/ is available at http://schmartyp7qtjzn7.onion/
Tor Browser Bundle
For end users (as opposed to servers running relays), it is recommended to use the Tor Browser bundle since it comes with a pre-configured web browser to protect your anonymity, and is self-contained.
While Tor Browser is running, it also servers as a local node and enables users to launch ad-hoc hidden services (e.g. OnionShare) or persistent ones [where the user retains the private key to a .onion domain that can even be publicized] (e.g. HiddenID).