'tor' is an implementation of The Onion Routing system, as
described in a bit more detail at http://www.onion-router.net/. You
can read list archives, and subscribe to the mailing list, at
http://archives.seul.org/or/dev/.

Is your question in the FAQ? Should it be?

Quickstart version for users:

0) Download the absolute newest version. No, really.
  http://freehaven.net/or/.
1) ./configure (or do the two-line version below, if you're on bsd)
2) make
3) cd src/config
4) ../or/or -f oprc -l debug&
5) download privoxy (www.privoxy.org), and add the line
  "forward-socks4a / localhost:9050 ." (without the quotes) to its
  config file.
6) point your mozilla (or whatever) to http proxy at localhost:8118 (this
  points it through Privoxy, so you now get good data-scrubbing too.)
7) make sure you've set it up correctly: go to
  http://www.junkbusters.com/cgi-bin/privacy and see what IP it says
  you're coming from.

More detailed version:

Dependencies:

  You're going to need Privoxy (www.privoxy.org) installed, and configured
  to point at a socks4a proxy -- see below.

  For tor itself, you're going to need openssl (0.9.5 or later
  -- including the dev stuff and includes). If you're on Linux,
  everything will probably work fine. OS X and BSD (but see below under
  troubleshooting) may work too. Let us know if you get it working
  elsewhere.

If you got the source from cvs:

  Run "./autogen.sh", which will run the various auto* programs and then
  run ./configure for you. From there, you should be able to run 'make'
  and you'll be on your way.

If you got the source from a tarball:

  Run ./configure and make as usual. There isn't much point in 
  'make install' yet.

If this doesn't work for you / troubleshooting:

  If you have problems finding libraries, try 
    CPPFLAGS="-I/usr/local/include" LDFLAGS="-L/usr/local/lib" \
    ./configure
  rather than simply ./configure.

  Check out the list archives at http://archives.seul.org/or/dev/ and see
  if somebody else has reported your problem. If not, please subscribe
  and let us know what you did to fix it, or give us the details and
  we'll see what we can do.

Do you want to run a tor server or a tor client?

  If you want to run a local onion proxy (that is, you're a user, not
  a node operator), go into src/config and look at the oprc file. (You
  shouldn't have to edit any of it.) You can run an onion proxy with
  "../or/or -f oprc". See below for how to use it.

  If you want to run a node in the tor network, use the orkeygen program
  (included) to generate a keypair:
    orkeygen file-for-privkey file-for-pubkey
  Then set up a config file for your node (start with sample-orrc
  and edit the top portion). Then take a look at the routers.or file,
  and mail arma@mit.edu an entry for your new router. You can start up
  your router with "../or/or -f you-orrc". Remember that you won't be
  able to authenticate to the other tor nodes until I've added you to
  the directory.

How to use it for web browsing:

  Download privoxy (www.privoxy.org). Install it. Add the following
  line to your 'config' file:
    forward-socks4a / localhost:9050 .
  Don't forget the . at the end.

  From here, you can point your browser/etc to localhost:8118 (as an
  httpd proxy) and your traffic will go through Privoxy, then through
  the onion proxy, to the onion routing network.

  You can also ignore the whole privoxy thing and set your Mozilla to
  use localhost 9050 directly as a socks4 server. But see doc/CLIENTS
  for why this may not give you the anonymity you want.

  For more convenient command-line use, I recommend making a ~/.wgetrc
  with the line
    http_proxy=http://localhost:8118
  Then you can do things like "wget seul.org" and watch as it downloads
  from the onion routing network.

  For fun, you can wget a very large file (a megabyte or more), and
  then ^z the wget a little bit in. The onion routers will continue
  talking for a while, queueing around 500k in the kernel-level buffers.
  When the kernel buffers are full, and the outbuf for the AP connection
  also fills, the internal congestion control will kick in and the exit
  connection will stop reading from the webserver. The circuit will
  wait until you fg the wget -- and other circuits will work just fine
  throughout. Then try ^z'ing the onion routers, and watch how well it
  recovers. Then try ^z'ing several of them at once. :)

How to use it for ssh:

  Download tsocks (tsocks.sourceforge.net) and configure it to talk to
  localhost:9050 as a socks4 server. My /etc/tsocks.conf simply has:
    server_port = 9050
    server = 127.0.0.1
  Then you can do "tsocks ssh arma@moria.mit.edu". But note that since
  ssh is suid root, you either need to do this as root, or cp a local
  version of ssh that isn't suid.