As I am sure many of you know, the Tor onion router is an amazing tool for anonymity. Sure it has it's caveats and cannot provide unbreakable protection but lets face it, nothing really can.
If you are new to Tor then I highly recommend downloading the Tor browser bundle for your OS. All you need to do is extract the files from the archive and run "start-tor-browser: % tar xvzf tor-browser-gnu-linux-i686-1.1.9-dev-en-US.tar.gz % cd tor-browser_en-US % ./start-tor-browser
or in windows, extract tor-browser_en-US and run the "Start Tor Browser" application. Go ahead and read any and all documentation you can find on the site. When it comes to hacking, knowledge is your friend.
Now that any beginners are caught up we can get to the more entertaining bit. We all know that Tor can be used to access the surface web by bouncing the connection through several relays to a Tor exit node. The only IP that is seen by the target site is that of the exit node. Tor has another functionality that is not as well known, that is Tor hidden services.
A Tor hidden service can be identified by a 16 char address with a .onion pseudo domain such as kpvz7ki2v5agwt35.onion As you will notice if you tried to put this address in your web browser, it is outside of the DNS root(you have to use Tor or tor2web although I recommend the first option for security reasons). Now when you start up your Tor browser and put in an .onion site you will be presented with a hidden website.(Please note that it may take several reloads to get the connection to go through as you are dealing with bandwidth issues inherent to the Tor network).
Assuming you entered the above given .onion site into your tor browser you should have been presented with the Hidden wiki. (now be careful because absolutely ANYONE can post here, be it the good or bad) Always keep in mind that your tor identity should never be linked to any email or web service that you contact during normal browsing.
From here you can start mining the darknet for new urls. Happy data mining =)
The only way a website can be found on the darknet is by being given a url, there aren't really any effective search engines to speak of. By mining the hidden wiki and a number of forums etc connected to it you can find a wide variety of information.